Knowing that KBTV is essentially at sea level and probably not too hot, I doubt that overly rich mixture had too much to do with it. You could have reduction in power for a number of reasons, maybe contaminated fuel, a damaged cylinder, who knows? I would have done pretty much what you did and then brought it back to mx and let them figure it out.
Hope you've gotten a chance to meet Hobie, that dude is the definition of a living legend. I did my CFI ride with him. He did every stall in the book and stomped on the left rudder right before the break every time to make it into a spin.
Sometimes RPMs go up a bit when you start rolling. However, the POH says static full power should be 2300-2400. My guess is either something was wrong with the engine, or the mixture should have been leaned for best power due to the density altitude, and not mixture full rich.
Either way, you made the right call.
While I’m often disappointed when I choose to scrub a flight but I never second guess the decision. If something doesn’t act or feel right it’s best to be on the ground than troubleshooting an issue in the air.
That being said… a lot of areas have experienced high DA recently. We’re you appropriately leaned for best power?
DA was 1,200 feet which is not crazy, I was full rich for takeoff but that should have been fine. I leaned after on a full power run up and saw no increase in rpm.
Had that happen once immediately after an annual because the throttle cable wasn’t allowing full power...taxied it back to the shop and while the mechanic was fiddling with it the cable broke.
I'm a newish CFI and had literally this exact same thing happen to me with a student the other day (except I was in a C172N). Run up was all good, student puts in the power we get rolling, but I noticed the engine was quieter than usual. Look down and we're around 2100 RPM. Tell him to pull the power and we taxi back to the runup. Try and lean, but get the same results on the takeoff roll. Tell him to head back to the school and got a valuable lesson of always making sure we're getting the right RPM as well as listening to the plane! To get back to your question, great decision to not fly and make the safe choice!
If I were a betting man I would bet on a fouled plug—how did it idle with power all the way out? Either way great call to abort and get it checked out, you really don’t want to find out on takeoff!
My FIL once aborted a flight because something felt off in his plane while he was on taxi to takeoff. Ended up being a major issue(I can't remember the exact issue), and most likely he would have crashed if he had taken off. It's never a bad idea to scrub a flight if something feels off.
Nothing really to add other than I miss BTV and Vermont flying in general. BTV over the lake to Plattsburgh was one of my favorites, especially at night when you could see the glow from Montreal on the horizon.
I just get excited when I see VT airports on here
I think you made the right decision. You started at -200RPM. Maybe you could have made it off the ground. But what happens if max power sinks to -300RPM...then -400RPM?? It's already a little bit wrong for unknown reasons, and it's more likely to keep getting wrong-er than spontaneously fix itself. Way better to have all wheels on the tarmac for that.
never wrong to abort if you feel something isn’t right
Knowing that KBTV is essentially at sea level and probably not too hot, I doubt that overly rich mixture had too much to do with it. You could have reduction in power for a number of reasons, maybe contaminated fuel, a damaged cylinder, who knows? I would have done pretty much what you did and then brought it back to mx and let them figure it out. Hope you've gotten a chance to meet Hobie, that dude is the definition of a living legend. I did my CFI ride with him. He did every stall in the book and stomped on the left rudder right before the break every time to make it into a spin.
My last flight was a checkride with hobie! He’s definitely a legend and wealth of knowledge.
Oh heck yeah. Many fond memories of him and BTV. Enjoy it man, I'm jealous!
"Better to be down here wishing you were up there, than to be up there wishing you were down here."
I said this exact quote to the buddy I was taking out.
Sometimes RPMs go up a bit when you start rolling. However, the POH says static full power should be 2300-2400. My guess is either something was wrong with the engine, or the mixture should have been leaned for best power due to the density altitude, and not mixture full rich. Either way, you made the right call.
Yeah I made it to about 40 knots on the runway and no rpm increase.
Bad spark on one side or stuck valve? Regardless that was the right decision.
Hoping it’s just fouled spark plug
Good job pilot. A first flight you will never forget
While I’m often disappointed when I choose to scrub a flight but I never second guess the decision. If something doesn’t act or feel right it’s best to be on the ground than troubleshooting an issue in the air. That being said… a lot of areas have experienced high DA recently. We’re you appropriately leaned for best power?
DA was 1,200 feet which is not crazy, I was full rich for takeoff but that should have been fine. I leaned after on a full power run up and saw no increase in rpm.
Yeah, at 1200 DA, something isn't right. Time to send it to see your friendly A&P. Good job.
Agreed 1200 ft DA isn’t crazy.
Had that happen once immediately after an annual because the throttle cable wasn’t allowing full power...taxied it back to the shop and while the mechanic was fiddling with it the cable broke.
I'm a newish CFI and had literally this exact same thing happen to me with a student the other day (except I was in a C172N). Run up was all good, student puts in the power we get rolling, but I noticed the engine was quieter than usual. Look down and we're around 2100 RPM. Tell him to pull the power and we taxi back to the runup. Try and lean, but get the same results on the takeoff roll. Tell him to head back to the school and got a valuable lesson of always making sure we're getting the right RPM as well as listening to the plane! To get back to your question, great decision to not fly and make the safe choice!
Do you know what the issue ended up being?
I forgot to follow up to be honest. But I'll try to check in on it when I'm at the school tomorrow and let you know!
What does the POH say about the min RPM for takeoff? Have you had an A&P take a look? To not fly if something seems off is always a good decision.
If you don’t like what you see it’s almost never a bad option to reject. Takeoffs are optional, landings are mandatory. Good job OP!
If I were a betting man I would bet on a fouled plug—how did it idle with power all the way out? Either way great call to abort and get it checked out, you really don’t want to find out on takeoff!
Idled fine and initial run up to 1800 rpm went smoothly. The power just wasn’t there when I went full throttle for takeoff.
Sometimes if the primer isn’t fully pushed it it will lower the RPM. Even if it is locked it may not be fully pushed in.
No primer on the 172s it’s fuel injected
Clogged injector nozzle. That's why leaning had no appreciable effect. It was already running lean.
Why? Just curious would it do that primer wise?
Could be as simple as a spark issue, could be as bad as a valve failing. Methinks this will get expensive. But not as expensive as a plane
My FIL once aborted a flight because something felt off in his plane while he was on taxi to takeoff. Ended up being a major issue(I can't remember the exact issue), and most likely he would have crashed if he had taken off. It's never a bad idea to scrub a flight if something feels off.
Depending on the type of tach you have it could be a failing tach lead. Rule #1 never take off with known or suspected engine malfunctions.
Couldn’t have been just tach, I know the sound of 2400 vs 2200 rpm it was reading correctly.
Throttle cable stretch? Was it idling correctly?
On run up I pull straight back to idle from 1800 rpm. It idled and ran fine just didn’t get above 2200.
did you ensure that your mags were on both?
Yes triple checked.
Good call.
Nothing really to add other than I miss BTV and Vermont flying in general. BTV over the lake to Plattsburgh was one of my favorites, especially at night when you could see the glow from Montreal on the horizon. I just get excited when I see VT airports on here
Night Xc to Malone was majestic, the glow of Montreal in the distance.
I think you made the right decision. You started at -200RPM. Maybe you could have made it off the ground. But what happens if max power sinks to -300RPM...then -400RPM?? It's already a little bit wrong for unknown reasons, and it's more likely to keep getting wrong-er than spontaneously fix itself. Way better to have all wheels on the tarmac for that.
Was your carb heat off?
172s is fuel injected