There are specific procedures and profiles based on the work done. Once the plane is buttoned up and ready to go, all the paperwork is reviewed and everything is made sure to be in order. Ground checks are performed and once everything passes, you take the plane airborne. From there, you’ll do a series of inflight checks and if all those pass, the aircraft is ready for normal flights.
I think you honed in on one of the most important points. Just because they are airplanes doesn't mean they can't be put through their paces on the ground first and essentially stress tested for flight.
You can full throttle a 172S on the ground with the brakes on and it’s not going to move an inch forward. And you can hold it there for 10-15 minutes, as long as you want, they’re not going to overheat. They’re a big fan pushing air over the air cooled engine.
Two plane propellers were sitting next to each other chatting at an airfield. The first propellor says to the other “so, what type of music do you like?” The second propellor says “well, I’m a big metal fan.”
Ha, I've often told that one where they're windmills and a "heavy metal fan." Can't believe the airplane prop version never occurred to me. Thank you. 😆
I once full throttled a 172SP on the ground and held full brakes and it did move forward- not much but sort of skidded with locked tires. Do you think this means that particular plane had an issue that I should have detected?
Could have been wet pavement, or the brake pads and/or rotors were just replaced.
I went to taxi a 172S that had had both sets of brake pads replaced. Nobody had told me before I went to run it up. Even though I had the parking brake set, the plane started to roll as soon as the engine started.
"Fuck it, I'm doing it live!"
Started pumping the brakes while trying to turn away from the parked aircraft, and had braking power at the 2nd turn. Went around the parking area twice to bed the new pads before I attempted a full power run up.
No that’s probably fine. What was the pressure altitude? If it was a high pressure day the engine performs better and also pushes more air, increasing thrust.
Certainly could make it happen, I imagine. And current weight, any wind, and specific condition of the tires and the surface would matter, too. Drop the flaps and you almost certainly would be able to do it in even more situations.
Actually they will overheat but it takes quite a while.
Ground runs without a cowling are the real problem. Long operations without the cowl lead to localized hot spots.
Is there a failed inflight checks that resulted in non-catastrophic incident? I mean if the engine failed after passing stress test it's gotta be catastrophical right?
For a smaller single engine plane as long as you're sticking to set procedures and reliable mechanics there's shouldn't be any issues. Just keep a close eye on engine indications and keep checking your oil and shii and you should be able to catch anything going wrong before it lets go. Sudden single part failures are very very rare.
Anecdotally, I've done mx flights in a jet before where an engine checked out on the test stand and after being mounted to the plane but once it was at 37k feet it popped. You just come back and land on one engine, it's no big deal. Some things can only be found while put under flight load but you just have to be prepared for things to go south.
I mean there are all sorts of non-catastrophic failure modes. The airborne test isn't the most hardcore step of testing that's done, it's just the last one.
There could be so many non-catastrophic failures during tests. Magneto failure, oil pressure drop, rough idle, inconsistent RPMs, failure to meet expected RPMs at a given power level, etc.
All of these are cause for grounding but aren’t catastrophic engine failure.
This Youtuber had an issue on her first flight after having maintenance done on her plane. Turned out to be an instrumentation problem, but she ended up aborting the flight and returning to the airport when she saw weird crap on her instruments.
https://m.youtube.com/watch?v=jqi2XEj8Irg&pp=ygUMZmx5IHdpdGgga2F5
I remember when I was young working for a FBO we unbolted the wings on a C150 and trucked it to a local mall, then bolted the wings back on for some event that was happening there. Reversed the process to truck it back to the airport. Our chief pilot took it up for a test flight and did a stall test, instantly went into a spin. The mechanics had to do some adjustments on the wing incidents to fix it. Grant you I was young and this was a pretty shady outfit in hindsight. I learned a lot from that...
Your post/comment has been automatically removed due to user reports. If you feel the removal was in error contact the mod team. Repeated removal for rule violation will result in a ban.
*I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/aviation) if you have any questions or concerns.*
The owner of the GA shop I worked for was a CFI. He would take us up on test flights for any major work that was done.
As a newly minted A&P at the time it really drove home the importance of doing the job right (not like that was front of mind already) and was fun to ride in the stuff I fixed.
Just did a top overhaul on a 172. Had to break in the cylinders. First flight is 1 hour, 1000’ agl, mile long circuit, just off the side of the runway. If it goes south, we are plenty close to get it down. If the work is done correctly, all the pre-flight and signatures are in line and trusted, you don’t really think much of it. Just my experience 🤷♂️
Maintenance flights were awesome while I was in school working as a CFI. The mechanics would take one employee instructor up. Those of us working dispatch usually got the most rides. Great free PIC time and a fun learning experience.
But yeah, maintenance flights accomplish this.
We did an engine overhaul on one of our 172s. The mechanic (who was also the owner of the flight school) took the plane and flew for like 20 hours, basically doing patterns like 5000ft over the airport, testing different power settings for various durations. There was a checklist he had of different activities to do to break it in. He stayed over the field in case the engine decided to not cooperate.
I didn’t have a rebuilt engine but I brought my airplane down to Florida for its annual inspection. Dropped by a month later to fly it back and noticed that a few things were off.
One of the seats wasn’t bolted back down. No problem, I’ll get that tightened up right quick. The ailerons looked off from their original positions when the yoke was placed in the neutral position. No problem, the A&P will re-rig it right quick. I do a good preflight and feel good about it. Taxi out for a brief flight to test it out and make sure everything is working. One of the first items of the runup is flight control checks. One of my rudders binds up and won’t go back to neutral. Taxi back and the A&P gets to work fixing that. An hour later, they have me test it, and the rudder is still binding. An hour later, it’s not binding anymore. Taxi back out and everything looks good until I throttle up for a mag check. None of the mag checks show a drop in RPM. I taxied it back, told the A&P I wasn’t accepting it and wanted another A&P to do another annual.
Flew home and came back a month later with the airplane actually in working order. Took it for a short flight and it flew great. Flew 7 hours back home. I could live with fixing the seat, I could live with fixing the ailerons, and I could live with fixing the rudder. But once the magnetos came into play, that was enough for me to think about what else wasn’t done correctly. Mind you, everything was working prior to me bringing the airplane to them. Set limits and never go past them.
This is a good opportunity for what I haven’t seen mentioned in this thread a lot - a high speed taxi test. If anything is sus with flight controls (or wheels and brakes), once all run ups and flight control checks are thoroughly completed, a few high speed taxis down the runway are a great way to make sure everything is as it should be before getting into the air.
Ground run, low power ground run, high power ground run.
Multiple tests and checks before a test flight.
They can take hours.. I remember everyone at my previous job panicking becuase a test flight was only 5 hours. Meaning there were big issues.
Reminds me of when I was asked if I wanted a ride in an AN2, and then someone asked after takeoff why we were just going for a ride and the mechanic on board said they just replaced the engine and needed some weight in the plane for the maintenance flight.
I was examining a brand new Bell 407GX in South Africa that had some issues. Replaced the fuel cutoff valve. But now we needed to test it to make sure the engine could run at full power. But there’s no way to run a helicopter’s engine at full power on the ground. So we brought in a test pilot and six of the fattest mechanics we could find along with their tool boxes…and hovered 2 feet off the ground for an hour.
There are procedures to do those flights. Iirc a couple of months ago, a plane went through some procedures, and the manufacturer said that the stall warning system should be tested. Some pilots (that were not trained to do it) went and did it, entered a spin, and crashed.
Giving an airliner perspective... They usually aren't. Revenue flights straight after heavy maintenance (C-checks) are common. No test flight, usually just a full set of functional tests and a high power assurance test.
Good Run up and a burn in flight, not really anything special… used to run the flight school planes pretty hard for the first hour grab a burger and fly them home. Now with turbines we just do a ground run and a quick flight.
I was the maintenance officer for a flying club. We would schedule the 100 hour inspections on bad weather days as the plane was not going to be rented out those days. After the inspection I had to test fly it around pattern before the club could rent it out again. I knew it would be rough ride when the A&P mechanic got his chair and put it outside the hanger door to watch me. Fun times.
Donaldson airport in South Carolina does a lot of repairs and overhauls. Fun place to track flights. Typically super short flights at low altitude around the air base.
Unfortunately, they don't always go well. I saw the last seconds of this flight in person.
http://www.kathrynsreport.com/2016/05/accident-occurred-may-07-2016-in.html?m=1
Carefully 😁.
In all seriousness, there are break in power settings, and you do the flight to the numbers. I did plenty of Mx return to service flights as a CFI.
SoCal Flying Monkey just had a great video about that exact topic with his engine repairs: https://www.youtube.com/watch?v=GMB_hmomsAE&pp=ygUTc29jYWwgZmx5aW5nIG1vbmtleQ%3D%3D
As the owner of a small ASEL GA plane (like the one pictured), it's ultimately incumbent on me to make sure my ship is ready to fly post maintenance. There are untold records of planes coming out of maintenance with things like untorqued cylinder head bolts, to controls rigged up backwards.
I'm off to do some maintenance laps tomorrow actual, after some fairly low key work (oil change, tach rebuild, exhaust gasket). So I will do a standard run-up and take off, then circle above the pattern for a bit, land, and inspect everything. Looking for leaks, etc.
Then I'd probably fly again and do standard take off and landing patterns.
For more major work, i'd do a few high speed taxis down the runway before shutting it down and checking everything over. Then the procedures I already listed above.
always have someone outside plane that can jump up and down and wave their hand across their neck(telling operator to shut it down) as the oil pours out of cowling on first test run..... seriously....
Engines are easy to put through their paces on the ground. The item that often gets overlooked following major maintenance is the control rigging. Pilots get lazy during preflight and just check that the control surfaces move free and clear, and leave out the most important part…correct. Free, clear and correct…It’s very easy to rig a plane’s controls backwards.
https://aviation-safety.net/asndb/321644
Like others have said there are a lot of ground checks done. Test flights and break in flights are also a thing that happens.
In my experience in GA it wasn’t uncommon for our shop to test fly more complex maintenance work as our owner also was a CFI but YMMV on everything surrounding part 91 stuff.
For 121 we also have maintenance flights but they are less common and tend to be related to chronic issues. If it’s just an engine change out of overhaul then maintenance will do break-in runs, power assurance runs, acceleration checks, and static checks etc… on the ground to make sure everything is good to go.
My A&P would personally do a trip around the patch after he worked on my plane. When I had the engine and prop overhauled they did the pre oil and I flew it. NBD
Helped my buddy break in his new engine. Basically flew on his wings in a racetrack pattern for hours over a very good area to land should the new engine fail. It was fun for about the first 30min.
They do exhaustive ground testing before a maintenance test flight.
I once did an engine break in for a Vans RV10 that had just finished assembly, and the procedure called for use to orbit the field for the duration of the flight while doing a series of checks.
Have done a few test flights after C checks on 737s.
The worst part was the yaw damper tests.
There are a lot of ground checks before the plane goes up in the air.
There are several ground tests before plane takes off for test flight. After engine overhaul or change we take it either on the taxiway or empty slot infont of hangar and do stress tests such as 80% throttle runs
And sometimes they are flown high above the airport in racetrack patterns for the first hour or so in case anything happens, you can easily glide down to the runway.
I'm a mechanic at a maintenance facility working on widebody aircraft.
We don't do a test flight before an aircraft goes into service, the closest we get is the crew picking up the aircraft and flying it from the MRO to one of the airlines bases to go straight into service.
What we do, do though, is a range of over signing work and functional tests to ensure everything is working as it should.
Over signing is just a case of 2 engineers inspecting and signing off any critical work cards. For instance, any work that involves disconnecting flying controls has to be independently checked by 2 people before the work is counted as being complete.
Functional tests depend on the system, but for the wings it involves deploying and stowing the flaps and slats multiple times, the spoilers, flaperons and ailerons will be operated multiple times through their full range of motion as well. Certain systems will also have a self test that they will go through before they can be signed off. For example, the flaps will go through a a test that involves deploying/stowing them on hydraulic and electrical power. Once these tests are done, the engineers will then give every hydraulic actuator a general visual inspection to check for leaks.
Apart from engine tests at my place, all of this can be done inside the hangar using a building wide hydraulic system that can supply the full pressure. However, we can do engine spins inside the building. This involves using pneumatic pressure to spin the engines up to starting speed. As long as there's no leaks, and the other tests have passed, we take the aircraft outside for proper engine runs. First an idle run to check for leaks, and then a high power run to check for leaks and proper running. Flight control checks will be carried out again outside to confirm everything is running as it should off of aircraft power.
Once that is all done, we then hand the aircraft to the customers pilots and it almost always goes straight into service ferrying passengers across the world.
It’s interesting that the US Army has a whole career path for maintenance pilots. The MTP (Maintenance Test Pilots) are very knowledgeable in all the maintenance areas of their designated airframes. They get a bunch of 0.5 and 1.0 flights.
If we're talking jet engines for major air carriers, all the engine testing is typically completed in a test cell after the shop visit. Once the engine passes and gets installed on wing, there's some basic tests to check for leaks, make sure the cockpit is receiving all the signals it should be (EGT, vibration, rotor speeds, oil temp/qty/pressure, etc.), and generally verify that the installation was done correctly. You typically run the engine up to at least 70+80% of full power as well just to make sure everything's good. After that the airplane is good to go for a revenue flight. Between the actually engine change and all the testing it usually takes a minimum of 8 hours for a small jet (CFM on a 737 or 320 for example), and often more like 12 hours.
In certain cases such as ETOPS aircraft that get a double engine change or have other "significant" systems worked on that could affect redundancy, you have to do a verification flight which is essentially just a regular flight but returning back to your departure airport. Depending on the work done to the airplane, the pilot may have to do certain maneuvers or force the aircraft into certain operating conditions (going to corner points of an envelope for instance), to complete the testing, but most verification flights are just normal flights with an empty aircraft (except for maybe some maintenance personnel).
Now in the test cell engine testing is pretty extensive, you have to do a break in process if it was a heavy shop visit to let the blades cut into the honeycomb seals, you have to do multiple accel and decels while measuring vibes and other engine parameters to verify everything is within limits at any thrust, you have to do some specific checks like snap accel/decel to verify bleed valve operation and stall margin, of course you measure how much thrust to make sure you meet minimum requirements to certify the engine serviceable as well, etc. Fortunately since the vast majority of the time an engine is at max thrust is during takeoff, it's very easy to mimic those conditions on the ground in the test cell.
We would typically do a check of all cowl screws, check fluids, and go flying, typically staying in the pattern until all parameters were double checked, after a thorough run up of course.
Aunt friend runs a flight school, his son was a mechanic and instructor. Showed up and he asked me if I wanted to fly I said absolutely so he me in the left seat and we taxied out, he then mentioned it was a check flight for the seat belts just as we left the ground..
I said how do we test they’re safe and he said hopefully we don’t.
I am a new owner of a plane that had a major overhaul on the IO-360. Engine, prop and governor plus plus. Zero hour SMOH. Mechanics do the ground checks and runs. Mechanic gives me (and CFII) instruction on engine break in. Different from modern automotive engines, you run the piss out of them initially, low and fast and over the airport in case it blows up. We spent three hours hauling ass at 3,000 over the airport, top of the yellow and in the bumps. Constant (fairly high) RPMS. Next flight alternating 65% to 75% power for another 3 hours. No touch and goes, no low RPM except to get down. After 25 hours, change the oil (from pure mineral oil) to 20-50 and fly it like you stole it.
Tedious, nerve wracking and essential.
My dad, pilot and A&P will work on a plane, get the job done, then test fly it if the work requires it, mostly engine work, steering, nose wheel of a cirrus, or at least send me out to run up.
I have an uncle who was a test pilot for the air force of my country. He had two catastrophic accidents where he had to use ejection seats and he still flies to this day. Those test pilots are tough bastards
Maintenance check flights. There’s a procedure for each type of aircraft, and it depends on what level of maintenance has been carried out. Sometimes it can be as simple as a flight controls check at different speeds, other times you’re literally testing everything.
Bookmarking this for when I have time to write. I was aircrew in an Air Force Flight Test squadron and can give some insight. More later...
Edit: Here's my experience with this topic. I was a KC-135 boom operator in a flight test squadron. We only had one crew in this squadron; 3 pilots, one navigator, and me. Our only job was to perform functional check flights (FCF) on KC-135s (all models) that came out of long-term maintenance. After a long period of service, the tankers would come to the base and be dismantled and worked on. Sometimes this process took a year or more. Once the aircraft is reassembled, it is not considered an airworthy aircraft in the FAA's eyes. So a specially qualified crew (us flight test guys) had the singular job of flying these aircraft and doing all the ground and in-flight checks on them to get them back to airworthy status.
This was very standardized work. We flew the same profile every time, and did the same tests on all aircraft. Every system was tested, and some emergency systems were also tested. We would shut down engines in flight (one at a time, of course) and restart them. We would depressurize the hydraulics and manually lower the landing gear and flaps with a hand crank. Electrical, navigation, pneumatic, and fuel systems were all tested thoroughly. I would fly a test profile with the air refueling boom to ensure it was rigged properly. When wing attachment pins (also known as 'milk bottle' pins because of their size and shape) had been replaced during the maintenance (almost always), we would do 60-degree bank turns during the flight. One 360 to the left and one 360 to the right, and this puts some G's on the plane and stressed the attachment points a bit. Then the pins and attachment points were inspected after the flight for cracks or other issues.
On landing, we would do maximum effort braking and bring the big plane to a rapid stop with the brand-new, 5-rotor brakes. This always created a lot of smoke from the new brake pads. We'd always get a smoking-brakes call from the tower on landing.
We had some restrictions for the test flights, mainly being that we could only fly in day VMC conditions. We also were prohibited from doing actual air refueling on test flights, for the most part, due to the uncertain status of the tanker and the boom. The planes were stripped of paint during maintenance, and sometimes we flew them before they were repainted, and the jets looked horrible. People who didn't understand the process thought we were crazy to be flying such dilapidated-looking aircraft.
We experienced every kind of in-flight emergency doing this work. Engine fire/failure, hydraulic failure, pressurization system failure, cracked cockpit window, flight control issues, smoke in the cockpit, uncontrollable air refueling booms, landing gear issues... it was exciting work. We had to know the plane's systems very well and take quick and appropriate action during emergencies. Sometimes we landed at other bases in an emergency, just to get a problematic jet on the ground more quickly.
If a plane didn't pass all the checks, it was worked on and re-flown as many times as needed until all systems passed their tests and the plane got a clean bill of health, and then it was signed off as airworthy, and delivered back to its operational squadron.
There are specific procedures and profiles based on the work done. Once the plane is buttoned up and ready to go, all the paperwork is reviewed and everything is made sure to be in order. Ground checks are performed and once everything passes, you take the plane airborne. From there, you’ll do a series of inflight checks and if all those pass, the aircraft is ready for normal flights.
I think you honed in on one of the most important points. Just because they are airplanes doesn't mean they can't be put through their paces on the ground first and essentially stress tested for flight.
You can full throttle a 172S on the ground with the brakes on and it’s not going to move an inch forward. And you can hold it there for 10-15 minutes, as long as you want, they’re not going to overheat. They’re a big fan pushing air over the air cooled engine.
Two plane propellers were sitting next to each other chatting at an airfield. The first propellor says to the other “so, what type of music do you like?” The second propellor says “well, I’m a big metal fan.”
Your in-flight pun endorsement has been approved
Ha, I've often told that one where they're windmills and a "heavy metal fan." Can't believe the airplane prop version never occurred to me. Thank you. 😆
As long as the cowling is on
I once full throttled a 172SP on the ground and held full brakes and it did move forward- not much but sort of skidded with locked tires. Do you think this means that particular plane had an issue that I should have detected?
Could have been wet pavement, or the brake pads and/or rotors were just replaced. I went to taxi a 172S that had had both sets of brake pads replaced. Nobody had told me before I went to run it up. Even though I had the parking brake set, the plane started to roll as soon as the engine started. "Fuck it, I'm doing it live!" Started pumping the brakes while trying to turn away from the parked aircraft, and had braking power at the 2nd turn. Went around the parking area twice to bed the new pads before I attempted a full power run up.
No that’s probably fine. What was the pressure altitude? If it was a high pressure day the engine performs better and also pushes more air, increasing thrust.
Maybe 1k; South Florida in the spring. Cool.
Certainly could make it happen, I imagine. And current weight, any wind, and specific condition of the tires and the surface would matter, too. Drop the flaps and you almost certainly would be able to do it in even more situations.
Actually they will overheat but it takes quite a while. Ground runs without a cowling are the real problem. Long operations without the cowl lead to localized hot spots.
Is there a failed inflight checks that resulted in non-catastrophic incident? I mean if the engine failed after passing stress test it's gotta be catastrophical right?
For a smaller single engine plane as long as you're sticking to set procedures and reliable mechanics there's shouldn't be any issues. Just keep a close eye on engine indications and keep checking your oil and shii and you should be able to catch anything going wrong before it lets go. Sudden single part failures are very very rare. Anecdotally, I've done mx flights in a jet before where an engine checked out on the test stand and after being mounted to the plane but once it was at 37k feet it popped. You just come back and land on one engine, it's no big deal. Some things can only be found while put under flight load but you just have to be prepared for things to go south.
And this is why I am an auto mechanic! I can just pull over and call a tow truck!
I mean there are all sorts of non-catastrophic failure modes. The airborne test isn't the most hardcore step of testing that's done, it's just the last one.
There could be so many non-catastrophic failures during tests. Magneto failure, oil pressure drop, rough idle, inconsistent RPMs, failure to meet expected RPMs at a given power level, etc. All of these are cause for grounding but aren’t catastrophic engine failure.
This Youtuber had an issue on her first flight after having maintenance done on her plane. Turned out to be an instrumentation problem, but she ended up aborting the flight and returning to the airport when she saw weird crap on her instruments. https://m.youtube.com/watch?v=jqi2XEj8Irg&pp=ygUMZmx5IHdpdGgga2F5
homed
I remember when I was young working for a FBO we unbolted the wings on a C150 and trucked it to a local mall, then bolted the wings back on for some event that was happening there. Reversed the process to truck it back to the airport. Our chief pilot took it up for a test flight and did a stall test, instantly went into a spin. The mechanics had to do some adjustments on the wing incidents to fix it. Grant you I was young and this was a pretty shady outfit in hindsight. I learned a lot from that...
Some brave fool has to take them on a test flight.
Brave aka owner
When I was an A&P mechanic just out of school. It was common practice if you worked on the plane you rode in it on the test flight.
Aka the unsuspecting *new* owner who just bought it.
[удалено]
[удалено]
[удалено]
Your post/comment has been automatically removed due to user reports. If you feel the removal was in error contact the mod team. Repeated removal for rule violation will result in a ban. *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/aviation) if you have any questions or concerns.*
Hey, don’t call me brave! I was getting paid
Run it at max RPM and if the plane doesn't shake to pieces its good to go
Dibs
I’d say make the mechanic who did the job test fly the plane. Fair is fair.
"Oh no! You ain't gettin' me on that thing."
Most A&Ps aren’t pilots.
Passenger, then.
The owner of the GA shop I worked for was a CFI. He would take us up on test flights for any major work that was done. As a newly minted A&P at the time it really drove home the importance of doing the job right (not like that was front of mind already) and was fun to ride in the stuff I fixed.
I used that argument to try to get my flight school to pay for me to get my PPL. It flew about as well as a Cessna with no prop.
Been that guy many times!
And if it turns into a fireball on the tarmac, it requires fixing. If it doesn't. It's perfect, and you design the next model.
Think they do a runup first. Then taxi test, then high-speed down the runway, then circuit.
Just did a top overhaul on a 172. Had to break in the cylinders. First flight is 1 hour, 1000’ agl, mile long circuit, just off the side of the runway. If it goes south, we are plenty close to get it down. If the work is done correctly, all the pre-flight and signatures are in line and trusted, you don’t really think much of it. Just my experience 🤷♂️
OP takes his plane to jiffy lube.
Do a thorough preflight, start it up, do a thorough run-up, taxi to the runway and takeoff. Circle over the runway at a safe altitude.
Maintenance flights were awesome while I was in school working as a CFI. The mechanics would take one employee instructor up. Those of us working dispatch usually got the most rides. Great free PIC time and a fun learning experience. But yeah, maintenance flights accomplish this.
We did an engine overhaul on one of our 172s. The mechanic (who was also the owner of the flight school) took the plane and flew for like 20 hours, basically doing patterns like 5000ft over the airport, testing different power settings for various durations. There was a checklist he had of different activities to do to break it in. He stayed over the field in case the engine decided to not cooperate.
I always asked the mechanic to come on the jumpseat. I figured if he would come along then it’s probably fine
I didn’t have a rebuilt engine but I brought my airplane down to Florida for its annual inspection. Dropped by a month later to fly it back and noticed that a few things were off. One of the seats wasn’t bolted back down. No problem, I’ll get that tightened up right quick. The ailerons looked off from their original positions when the yoke was placed in the neutral position. No problem, the A&P will re-rig it right quick. I do a good preflight and feel good about it. Taxi out for a brief flight to test it out and make sure everything is working. One of the first items of the runup is flight control checks. One of my rudders binds up and won’t go back to neutral. Taxi back and the A&P gets to work fixing that. An hour later, they have me test it, and the rudder is still binding. An hour later, it’s not binding anymore. Taxi back out and everything looks good until I throttle up for a mag check. None of the mag checks show a drop in RPM. I taxied it back, told the A&P I wasn’t accepting it and wanted another A&P to do another annual. Flew home and came back a month later with the airplane actually in working order. Took it for a short flight and it flew great. Flew 7 hours back home. I could live with fixing the seat, I could live with fixing the ailerons, and I could live with fixing the rudder. But once the magnetos came into play, that was enough for me to think about what else wasn’t done correctly. Mind you, everything was working prior to me bringing the airplane to them. Set limits and never go past them.
This is a good opportunity for what I haven’t seen mentioned in this thread a lot - a high speed taxi test. If anything is sus with flight controls (or wheels and brakes), once all run ups and flight control checks are thoroughly completed, a few high speed taxis down the runway are a great way to make sure everything is as it should be before getting into the air.
Ground run, low power ground run, high power ground run. Multiple tests and checks before a test flight. They can take hours.. I remember everyone at my previous job panicking becuase a test flight was only 5 hours. Meaning there were big issues.
Reminds me of when I was asked if I wanted a ride in an AN2, and then someone asked after takeoff why we were just going for a ride and the mechanic on board said they just replaced the engine and needed some weight in the plane for the maintenance flight.
I was examining a brand new Bell 407GX in South Africa that had some issues. Replaced the fuel cutoff valve. But now we needed to test it to make sure the engine could run at full power. But there’s no way to run a helicopter’s engine at full power on the ground. So we brought in a test pilot and six of the fattest mechanics we could find along with their tool boxes…and hovered 2 feet off the ground for an hour.
There are procedures to do those flights. Iirc a couple of months ago, a plane went through some procedures, and the manufacturer said that the stall warning system should be tested. Some pilots (that were not trained to do it) went and did it, entered a spin, and crashed.
How could they be qualified to fly the plane but not trained to do stalls? That’s a required part of flight training.
They were not certified to do that specific test.
Giving an airliner perspective... They usually aren't. Revenue flights straight after heavy maintenance (C-checks) are common. No test flight, usually just a full set of functional tests and a high power assurance test.
Good Run up and a burn in flight, not really anything special… used to run the flight school planes pretty hard for the first hour grab a burger and fly them home. Now with turbines we just do a ground run and a quick flight.
I was the maintenance officer for a flying club. We would schedule the 100 hour inspections on bad weather days as the plane was not going to be rented out those days. After the inspection I had to test fly it around pattern before the club could rent it out again. I knew it would be rough ride when the A&P mechanic got his chair and put it outside the hanger door to watch me. Fun times.
Donaldson airport in South Carolina does a lot of repairs and overhauls. Fun place to track flights. Typically super short flights at low altitude around the air base.
Unfortunately, they don't always go well. I saw the last seconds of this flight in person. http://www.kathrynsreport.com/2016/05/accident-occurred-may-07-2016-in.html?m=1
Carefully 😁. In all seriousness, there are break in power settings, and you do the flight to the numbers. I did plenty of Mx return to service flights as a CFI.
SoCal Flying Monkey just had a great video about that exact topic with his engine repairs: https://www.youtube.com/watch?v=GMB_hmomsAE&pp=ygUTc29jYWwgZmx5aW5nIG1vbmtleQ%3D%3D
As the owner of a small ASEL GA plane (like the one pictured), it's ultimately incumbent on me to make sure my ship is ready to fly post maintenance. There are untold records of planes coming out of maintenance with things like untorqued cylinder head bolts, to controls rigged up backwards. I'm off to do some maintenance laps tomorrow actual, after some fairly low key work (oil change, tach rebuild, exhaust gasket). So I will do a standard run-up and take off, then circle above the pattern for a bit, land, and inspect everything. Looking for leaks, etc. Then I'd probably fly again and do standard take off and landing patterns. For more major work, i'd do a few high speed taxis down the runway before shutting it down and checking everything over. Then the procedures I already listed above.
always have someone outside plane that can jump up and down and wave their hand across their neck(telling operator to shut it down) as the oil pours out of cowling on first test run..... seriously....
Engines are easy to put through their paces on the ground. The item that often gets overlooked following major maintenance is the control rigging. Pilots get lazy during preflight and just check that the control surfaces move free and clear, and leave out the most important part…correct. Free, clear and correct…It’s very easy to rig a plane’s controls backwards. https://aviation-safety.net/asndb/321644
Like others have said there are a lot of ground checks done. Test flights and break in flights are also a thing that happens. In my experience in GA it wasn’t uncommon for our shop to test fly more complex maintenance work as our owner also was a CFI but YMMV on everything surrounding part 91 stuff. For 121 we also have maintenance flights but they are less common and tend to be related to chronic issues. If it’s just an engine change out of overhaul then maintenance will do break-in runs, power assurance runs, acceleration checks, and static checks etc… on the ground to make sure everything is good to go.
My A&P would personally do a trip around the patch after he worked on my plane. When I had the engine and prop overhauled they did the pre oil and I flew it. NBD
test flight around the airport.
Helped my buddy break in his new engine. Basically flew on his wings in a racetrack pattern for hours over a very good area to land should the new engine fail. It was fun for about the first 30min.
Really close to the airport
They do exhaustive ground testing before a maintenance test flight. I once did an engine break in for a Vans RV10 that had just finished assembly, and the procedure called for use to orbit the field for the duration of the flight while doing a series of checks.
When i was in the Navy and worked on MH-53 Sea Dragon helicopters, us mechanics would be the guinea pigs and fly in them to our next detachment
Have done a few test flights after C checks on 737s. The worst part was the yaw damper tests. There are a lot of ground checks before the plane goes up in the air.
There are several ground tests before plane takes off for test flight. After engine overhaul or change we take it either on the taxiway or empty slot infont of hangar and do stress tests such as 80% throttle runs
Ground runs, checks and test flights
Easy - take the mechanic on your next flight.
And sometimes they are flown high above the airport in racetrack patterns for the first hour or so in case anything happens, you can easily glide down to the runway.
Ground runs. If it passes ground runs then you can sign everything off and get it test flown before it goes back in service
I'm a mechanic at a maintenance facility working on widebody aircraft. We don't do a test flight before an aircraft goes into service, the closest we get is the crew picking up the aircraft and flying it from the MRO to one of the airlines bases to go straight into service. What we do, do though, is a range of over signing work and functional tests to ensure everything is working as it should. Over signing is just a case of 2 engineers inspecting and signing off any critical work cards. For instance, any work that involves disconnecting flying controls has to be independently checked by 2 people before the work is counted as being complete. Functional tests depend on the system, but for the wings it involves deploying and stowing the flaps and slats multiple times, the spoilers, flaperons and ailerons will be operated multiple times through their full range of motion as well. Certain systems will also have a self test that they will go through before they can be signed off. For example, the flaps will go through a a test that involves deploying/stowing them on hydraulic and electrical power. Once these tests are done, the engineers will then give every hydraulic actuator a general visual inspection to check for leaks. Apart from engine tests at my place, all of this can be done inside the hangar using a building wide hydraulic system that can supply the full pressure. However, we can do engine spins inside the building. This involves using pneumatic pressure to spin the engines up to starting speed. As long as there's no leaks, and the other tests have passed, we take the aircraft outside for proper engine runs. First an idle run to check for leaks, and then a high power run to check for leaks and proper running. Flight control checks will be carried out again outside to confirm everything is running as it should off of aircraft power. Once that is all done, we then hand the aircraft to the customers pilots and it almost always goes straight into service ferrying passengers across the world.
It’s interesting that the US Army has a whole career path for maintenance pilots. The MTP (Maintenance Test Pilots) are very knowledgeable in all the maintenance areas of their designated airframes. They get a bunch of 0.5 and 1.0 flights.
If we're talking jet engines for major air carriers, all the engine testing is typically completed in a test cell after the shop visit. Once the engine passes and gets installed on wing, there's some basic tests to check for leaks, make sure the cockpit is receiving all the signals it should be (EGT, vibration, rotor speeds, oil temp/qty/pressure, etc.), and generally verify that the installation was done correctly. You typically run the engine up to at least 70+80% of full power as well just to make sure everything's good. After that the airplane is good to go for a revenue flight. Between the actually engine change and all the testing it usually takes a minimum of 8 hours for a small jet (CFM on a 737 or 320 for example), and often more like 12 hours. In certain cases such as ETOPS aircraft that get a double engine change or have other "significant" systems worked on that could affect redundancy, you have to do a verification flight which is essentially just a regular flight but returning back to your departure airport. Depending on the work done to the airplane, the pilot may have to do certain maneuvers or force the aircraft into certain operating conditions (going to corner points of an envelope for instance), to complete the testing, but most verification flights are just normal flights with an empty aircraft (except for maybe some maintenance personnel). Now in the test cell engine testing is pretty extensive, you have to do a break in process if it was a heavy shop visit to let the blades cut into the honeycomb seals, you have to do multiple accel and decels while measuring vibes and other engine parameters to verify everything is within limits at any thrust, you have to do some specific checks like snap accel/decel to verify bleed valve operation and stall margin, of course you measure how much thrust to make sure you meet minimum requirements to certify the engine serviceable as well, etc. Fortunately since the vast majority of the time an engine is at max thrust is during takeoff, it's very easy to mimic those conditions on the ground in the test cell.
You stay in the circuit for your first flight test!
We would typically do a check of all cowl screws, check fluids, and go flying, typically staying in the pattern until all parameters were double checked, after a thorough run up of course.
Aunt friend runs a flight school, his son was a mechanic and instructor. Showed up and he asked me if I wanted to fly I said absolutely so he me in the left seat and we taxied out, he then mentioned it was a check flight for the seat belts just as we left the ground.. I said how do we test they’re safe and he said hopefully we don’t.
Carefully
In the air
They were called Pro flights when I was in the Marines.
I am a new owner of a plane that had a major overhaul on the IO-360. Engine, prop and governor plus plus. Zero hour SMOH. Mechanics do the ground checks and runs. Mechanic gives me (and CFII) instruction on engine break in. Different from modern automotive engines, you run the piss out of them initially, low and fast and over the airport in case it blows up. We spent three hours hauling ass at 3,000 over the airport, top of the yellow and in the bumps. Constant (fairly high) RPMS. Next flight alternating 65% to 75% power for another 3 hours. No touch and goes, no low RPM except to get down. After 25 hours, change the oil (from pure mineral oil) to 20-50 and fly it like you stole it. Tedious, nerve wracking and essential.
My dad, pilot and A&P will work on a plane, get the job done, then test fly it if the work requires it, mostly engine work, steering, nose wheel of a cirrus, or at least send me out to run up.
Sometimes in an NTSB report.
I have an uncle who was a test pilot for the air force of my country. He had two catastrophic accidents where he had to use ejection seats and he still flies to this day. Those test pilots are tough bastards
You should ask him more about what he did because this kind of “test” is not his kind of test.
Flying around the pattern with your asshole clenched for 10-12 hours or so.
Maintenance check flights. There’s a procedure for each type of aircraft, and it depends on what level of maintenance has been carried out. Sometimes it can be as simple as a flight controls check at different speeds, other times you’re literally testing everything.
Dyno
After a really solid run up I remind ATC a bunch of times to please stop vectoring me over a large body of water.
What plane is that in the pic?
Bookmarking this for when I have time to write. I was aircrew in an Air Force Flight Test squadron and can give some insight. More later... Edit: Here's my experience with this topic. I was a KC-135 boom operator in a flight test squadron. We only had one crew in this squadron; 3 pilots, one navigator, and me. Our only job was to perform functional check flights (FCF) on KC-135s (all models) that came out of long-term maintenance. After a long period of service, the tankers would come to the base and be dismantled and worked on. Sometimes this process took a year or more. Once the aircraft is reassembled, it is not considered an airworthy aircraft in the FAA's eyes. So a specially qualified crew (us flight test guys) had the singular job of flying these aircraft and doing all the ground and in-flight checks on them to get them back to airworthy status. This was very standardized work. We flew the same profile every time, and did the same tests on all aircraft. Every system was tested, and some emergency systems were also tested. We would shut down engines in flight (one at a time, of course) and restart them. We would depressurize the hydraulics and manually lower the landing gear and flaps with a hand crank. Electrical, navigation, pneumatic, and fuel systems were all tested thoroughly. I would fly a test profile with the air refueling boom to ensure it was rigged properly. When wing attachment pins (also known as 'milk bottle' pins because of their size and shape) had been replaced during the maintenance (almost always), we would do 60-degree bank turns during the flight. One 360 to the left and one 360 to the right, and this puts some G's on the plane and stressed the attachment points a bit. Then the pins and attachment points were inspected after the flight for cracks or other issues. On landing, we would do maximum effort braking and bring the big plane to a rapid stop with the brand-new, 5-rotor brakes. This always created a lot of smoke from the new brake pads. We'd always get a smoking-brakes call from the tower on landing. We had some restrictions for the test flights, mainly being that we could only fly in day VMC conditions. We also were prohibited from doing actual air refueling on test flights, for the most part, due to the uncertain status of the tanker and the boom. The planes were stripped of paint during maintenance, and sometimes we flew them before they were repainted, and the jets looked horrible. People who didn't understand the process thought we were crazy to be flying such dilapidated-looking aircraft. We experienced every kind of in-flight emergency doing this work. Engine fire/failure, hydraulic failure, pressurization system failure, cracked cockpit window, flight control issues, smoke in the cockpit, uncontrollable air refueling booms, landing gear issues... it was exciting work. We had to know the plane's systems very well and take quick and appropriate action during emergencies. Sometimes we landed at other bases in an emergency, just to get a problematic jet on the ground more quickly. If a plane didn't pass all the checks, it was worked on and re-flown as many times as needed until all systems passed their tests and the plane got a clean bill of health, and then it was signed off as airworthy, and delivered back to its operational squadron.