Flap retraction during landing roll
- Thread starter ColMustard
- Start date
tonyw
Well-Known Member
I have a POH for a 1982 C172N right here.
At 20 degrees Celsius, at sea level, it takes 1295 feet to land over a 50 foot obstacle, with a ground roll of 550 feet. On the other hand, it takes 1685 feet to take off over a 50 foot obstacle, with a ground roll of 925 feet.
Pretty cut and dried if you ask me.
At 20 degrees Celsius, at sea level, it takes 1295 feet to land over a 50 foot obstacle, with a ground roll of 550 feet. On the other hand, it takes 1685 feet to take off over a 50 foot obstacle, with a ground roll of 925 feet.
Pretty cut and dried if you ask me.
Mavmb
Well-Known Member
I always teach to clean the flaps up after touch down. I agree the braking action from flaps up or down is probably negligible. However, at least in little planes, it a very important habit to clean the flaps up right after touchdown. If this habit does not become a reflex for students doing touch and goes, than one of those times they forget to take the flaps up, and before they know it, they are crashing after attempting a full flap take off!
The other reason I always teach cleaning the flaps up is the much better control you get with flaps up while rolling on the ground, especially if it is windy. I think it is the control factor that makes pilots feel like they are decelerating so much more with the flaps up. It's the same reason we don't land with full flaps when it is windy. And as far as the argument goes about how using the flap lever breaks concentration, well if you can't lift one lever for a split second without breaking your concentration, than maybe piloting isn't the best career or hobby for you!
The other reason I always teach cleaning the flaps up is the much better control you get with flaps up while rolling on the ground, especially if it is windy. I think it is the control factor that makes pilots feel like they are decelerating so much more with the flaps up. It's the same reason we don't land with full flaps when it is windy. And as far as the argument goes about how using the flap lever breaks concentration, well if you can't lift one lever for a split second without breaking your concentration, than maybe piloting isn't the best career or hobby for you!
Chris_Ford
Well-Known Member
SteveC said:Did ya?
No, I didn't
hattrick
Well-Known Member
first off dugie im sorry if i misunderstood you. i am relatively unfumiliar with the pa28 so i assumed that 25* of flaps was flaps at the landing position and not takeoff position. does the POH call for 25* for any type of takeoff in this particular airplane. if not then you may reconsider leaving them at 25. i did not say or intend to imply that taking off with flaps was a bad idea. i do that daily and if i didnt i would not be alive today. however using more than what is approved could get you in trouble. the carb heat thing. i think we have all forgot to put it in before and its worked just fine but i dont think its a good habit to get into. it could be the deciding factor some day on whether or not we get off the ground in time.
i am not trying to get into a pissing match here its just that i fly in a world that requires things to be done a certain way or we are screwed. we dont have enough runway to make mistakes. im assuming you know exactly what your plane can do its more the concern of letting some of these youngsters know that taking off with flaps in the landing position just because you dont want to or forgot to retract them(evidently not the case in the pa28 with 25*) can kill you. ive seen it happen
i am not trying to get into a pissing match here its just that i fly in a world that requires things to be done a certain way or we are screwed. we dont have enough runway to make mistakes. im assuming you know exactly what your plane can do its more the concern of letting some of these youngsters know that taking off with flaps in the landing position just because you dont want to or forgot to retract them(evidently not the case in the pa28 with 25*) can kill you. ive seen it happen
ColMustard
New Member
Mavmb said:
Actually it happens to the best of us. Students will begin to bank to the right or left all the time while looking inside the cockpit to review their sectional. It can and does happen on the ground as well, especially if their attention is divided.
I actually just had this discussion with the chief of flight ops. here at my work. The touch and go's discussion is not necessarily related here, because we are bringing the flaps up to prevent us from taking off with 30 degrees. The argument is more about bringing flaps up to transfer weight to the wheels on landing. The point came up that speed is everything, and on short field ops we want to land as slow as possible right? Well if that were the case flaps will have little impact on dramatically decreasing the landing distance. The emphasis is to land on your spot with minimal airspeed.
But.......there are cases where a flap reduction will help out, but it should not be a reflex, it should be a decision based on that particular scenario. A reflex would be more in line with reducing the AoA during a stall recovery.
Never thought this discussion would run this long, but a lot of good points!
-ColM
tonyw
Well-Known Member
I went up with a DPE as my safety pilot, and out of habit, when I stopped on the runway, I pushed in the carb heat and retracted the flaps. He said that it was a good thing I wasn't doing that on a checkride, because while he wouldn't bust me for it, he'd sure say something about it.
And I thought about it, and he's right. I should get my ass off the runway, and get out of people's way, and then clean up the airplane.
And I thought about it, and he's right. I should get my ass off the runway, and get out of people's way, and then clean up the airplane.
Dugie8
Well-Known Member
tonyw said:
EXACTLY! At almost airline or corporate, or whatever, gig you work at, cleaning up the airplane happens OFF the runway. Biggest reason, your attention is on the driving the airplane (both the PF and the PNF) and two changing flaps also changes rudder throw on some airplanes and that can be very very bad jooojooo if you are trying to make a sharp turn with the rudders and POOOF its gone.
Touch and goes are not supposed to be performance landings (ie soft or short field landings) they are used to build proficiency in landing. If you are trying to build proficiency the last thing you need to be doing is playing with the airplanes config. Land with approach flaps if your airplane has that setting, otherwise, practice your no flappers. Carb heat, if icing is that big of a concern, land without the carb heat, then turn it on during the upwind and leave it until final and turn it off. In 3 years of instruction in ND I had carb ice ONCE, in a seminole in the clouds when I was too distracted with my student and his setting up of an approach using those stupid 5 Ts and such. Not to say carb ice is not a big issue, but it does take a bit of time to happen.
seagull
Well-Known Member
Why did you stop on the runway?
Not to get into this somewhat inane debate, but to answer the question on spoilers on larger aircraft, the reasons for using those instead of flaps is simple:
1. They are installed anyway to help slow down/go down, plus roll control and backup roll control;
2. The deploy a LOT faster than you could get flaps up;
3. Even with flaps up, you still develop some lift, with spoilers they kill all the lift on the effected areas, flaps or not;
4. With the flaps now not adding any lift, they are still increasing the drag
5. In the event of a go-around after runway contact, you don't want the flaps to be up, as a big airplane won't get airborne in the runway available, not to mention tire speed limitations!
There are probably more reasons than that, but there's a quick list! Incidentally, wrapped in some of the above issues are also why it's not THAT big of a deal in light aircraft, particularly fixed gear where you are trying to stop on a very short field and it is not out of compliance with the manufacturers recommendations.
Not to get into this somewhat inane debate, but to answer the question on spoilers on larger aircraft, the reasons for using those instead of flaps is simple:
1. They are installed anyway to help slow down/go down, plus roll control and backup roll control;
2. The deploy a LOT faster than you could get flaps up;
3. Even with flaps up, you still develop some lift, with spoilers they kill all the lift on the effected areas, flaps or not;
4. With the flaps now not adding any lift, they are still increasing the drag
5. In the event of a go-around after runway contact, you don't want the flaps to be up, as a big airplane won't get airborne in the runway available, not to mention tire speed limitations!
There are probably more reasons than that, but there's a quick list! Incidentally, wrapped in some of the above issues are also why it's not THAT big of a deal in light aircraft, particularly fixed gear where you are trying to stop on a very short field and it is not out of compliance with the manufacturers recommendations.
Mavmb
Well-Known Member
You guys are cracking me up! You all, y'all are talking so much about getting off the runway, that you stop flying the airplane on the runway to avoid breaking your concentration!!! We are talking about a flap lever after touching down guys! You don't even have to look away from the runway! Hand goes from throttle to flap lever in a Cessna, fraction of a second. Or a Piper, drop flap lever, even easier. Not like we are tuning radios after landing! Lol, maybe we shouldn't use brakes after landing either, might be too distracting!
Chris_Ford
Well-Known Member
C172SP POH:
T/o ground roll 745
50' : 1275
ldg ground roll: 545
50': 1290...
Conditions: Max gross, sea level, ISA. As weight decreases on t/o, the ground roll decreases dramatically (610' at 2200 lbs)... But notice that the 50' distance on the landing is larger than takeoff, which is somewhat surprising.
I think we can agree to compromise and say "it requires essentially the same amount" seeing as varying situations could lean towards one or the other, agreed?
T/o ground roll 745
50' : 1275
ldg ground roll: 545
50': 1290...
Conditions: Max gross, sea level, ISA. As weight decreases on t/o, the ground roll decreases dramatically (610' at 2200 lbs)... But notice that the 50' distance on the landing is larger than takeoff, which is somewhat surprising.
I think we can agree to compromise and say "it requires essentially the same amount" seeing as varying situations could lean towards one or the other, agreed?
Oh no you don't. Not getting off that easy.Chris_Ford said:
I would "compromise" if that relationship stayed the same for the rest of chart, but I'm pretty sure that at any higher altitude or higher temperature the take-off distance will always be longer than landing, mostly much longer. The only times that take-off might be shorter is when at low temp, sea level, and light weights, and even then it will be close. Majority of the time, by far, take-off will take lots more room.
How say thee?
(Actually you (sorta) won one bet already. I figured you'd take one look at the charts and hope this thread went quietly away and I wouldn't hear back from you here. Good man for coming back to it.
)
ColMustard
New Member
I think we might be forgetting the fact that though the landing distance should be shorter than t/o distance, I think most of us try to land the plane first, then slow as necessary.
The figures in the POH are determined after several test runs . But how do they measure landing distance? I assume they average the distance from when the aircraft touches the runway to the point the airplane STOPS on the runway. So even though we could land and stop in the distance shown in the Performance section, most of us (on normal landings) slow the aircraft to a safe speed to turn off the runway at the nearest intersection.
This may be the reason why the t/o distance may seem shorter compared to landing distance. But the aircraft is still capable to land and stop in a shorter distance compared to t/o. (in MOST cases at least)
The numbers don't lie!
-ColM
The figures in the POH are determined after several test runs . But how do they measure landing distance? I assume they average the distance from when the aircraft touches the runway to the point the airplane STOPS on the runway. So even though we could land and stop in the distance shown in the Performance section, most of us (on normal landings) slow the aircraft to a safe speed to turn off the runway at the nearest intersection.
This may be the reason why the t/o distance may seem shorter compared to landing distance. But the aircraft is still capable to land and stop in a shorter distance compared to t/o. (in MOST cases at least)
The numbers don't lie!
-ColM
Chris_Ford
Well-Known Member
SteveC said:(Actually you (sorta) won one bet already. I figured you'd take one look at the charts and hope this thread went quietly away and I wouldn't hear back from you here. Good man for coming back to it.
Yeah well thanks to Mav I saw the thread at work and light bulb came on. Now that I'm back home I can't reference it so we'll have to wait another week before I remember again
Nick
Well-Known Member
Champcar said:
I don't consider raising the flaps after touchdown having fun in the airplane...other things are fun to me than that moment. But the point everyone is making is that it doesn't DO anything. You are giving yourself a distraction for no reason!
Champcar said:
Unless you are renting an airplane, in which case you should fly it how the owner/FBO wants you to fly it.
Champcar
Well-Known Member
What distraction.. most of us can raise the flaps without ever thinking of how to do it. In that case i might as well not make a wind correctiong or rudder correction casue it might distract me from rolling down the runway. Some people take things way too seriously.Nick said:
I rent an airplane as a Private Pilot and I fly it how i fly it.