Thrust to flare?
Thread Starter
Join Date: Oct 2006
Location: Ankh Morpork, DW
Posts: 652
Likes: 0
Received 0 Likes
on
0 Posts
Well, I flew another sector with said pilot, and I asked him about his background: 727 (FE), DC-9, MD-80, and 737.
I'll estimate I've flown with well over 300 pilots on the 737, but for simple math: 300 pilots and 3 of which use this technique. 1% use this technique. I've flown with many former 727 and DC-9 pilots who do not use this technique.
The last leg we flew, he jockeyed the power around 40-60+ % in the flare-float and took the jet to the end of the runway. There was no shear/gust/high sink.
Not impressed with this technique, but thanks to all for the interesting input.
I'll estimate I've flown with well over 300 pilots on the 737, but for simple math: 300 pilots and 3 of which use this technique. 1% use this technique. I've flown with many former 727 and DC-9 pilots who do not use this technique.
The last leg we flew, he jockeyed the power around 40-60+ % in the flare-float and took the jet to the end of the runway. There was no shear/gust/high sink.
Not impressed with this technique, but thanks to all for the interesting input.
Join Date: Oct 2007
Location: fort sheridan, il
Posts: 1,656
Likes: 0
Received 0 Likes
on
0 Posts
crunk...one thing I have learned about pilots is this:
at some point, you get the sweetest landing you ever had and you used an unusual technique. so, somehow you think...gee if` i can only do that again
and they use a nutty technique...just hoping.
well, they got lucky once, but they learned to be stupid.
I knew a dc9 captain who trimmed into the flare on every landing...his landings wer pretty good...but I told him that if I was the captain I would tell him not to do it that way as the technique will bite you in the butt one day.
you might even use the same phrasing to tell the pilot he is wrong.
once in awhile a burst of thrust does save things...but to do it all the time may mean he has vision problems!
at some point, you get the sweetest landing you ever had and you used an unusual technique. so, somehow you think...gee if` i can only do that again
and they use a nutty technique...just hoping.
well, they got lucky once, but they learned to be stupid.
I knew a dc9 captain who trimmed into the flare on every landing...his landings wer pretty good...but I told him that if I was the captain I would tell him not to do it that way as the technique will bite you in the butt one day.
you might even use the same phrasing to tell the pilot he is wrong.
once in awhile a burst of thrust does save things...but to do it all the time may mean he has vision problems!
Join Date: Oct 2010
Location: Germany
Age: 47
Posts: 402
Likes: 0
Received 0 Likes
on
0 Posts
the pilot jams the T/L forward and pulls it back just as rapidly. It wasn't for a gust, just for. . . ?
Join Date: Mar 2011
Location: engineer at large
Posts: 1,409
Likes: 0
Received 0 Likes
on
0 Posts
For the "long" 737 like the 800, 900 (and even the 300 maybe) the flare is sensitive and that's not easy to decrease the sink rate below 200/150 ft per minute (that should give you a standard load) with flaps at 40, but quite easy if you keep some thrust til touch down.
When I was on the 747 Classic freighters if we were up around the 285 tonne max landing weight I'd start the flare when the 30' auto call was made and leave the approach power on until the nose had pitched that 2° pitch more up, then pull the power off and it'd settle nicely.
Down around the 180 tonne mark, cut the power at the 20' call and pitch, etc.
Down around the 180 tonne mark, cut the power at the 20' call and pitch, etc.
What the power on crowd don't see is that you are basically 'powering into the ground'
This will nearly always produce a harder landing than the manufacturer's recommended idle thrust touchdown.
I doubt there is a flight manual out there that recommends (outside of correcting a last minute high sink rate) landing with other than idle thrust on a jet transport.
This will nearly always produce a harder landing than the manufacturer's recommended idle thrust touchdown.
I doubt there is a flight manual out there that recommends (outside of correcting a last minute high sink rate) landing with other than idle thrust on a jet transport.
Psychophysiological entity
Whether we know it or not, we react to seat of the pants sink. At least, I hope we do. Trees mentioned some posts ago. Hangers, or a mischievous wind, you can't plan for it. A sudden sink towards the concrete would get a power reaction from me, even before it had registered in my higher thinking processes. 
As is evidenced by:
My pants never gave me clues in a sim.
As is evidenced by:
Interestingly, you don't see much of this technique in the simulator
Join Date: Aug 2006
Location: Asia
Posts: 75
Likes: 0
Received 0 Likes
on
0 Posts
This is definitely not a normal technique, but can be used when landing on a longish runway and having a high sink rate during the flare due to a loss of energy over threshold (caused by all sorts of different factors, but commonly a loss of headwind). I find a small well timed increase in thrust can reduce the rate of descent on the B737 NG. The under slung CFM 56's produce quite a large thrust / pitch coupling, so this small increase in thrust does two things to reduce the ROD. 1) Replaces lost energy 2) Small increase in pitch attitude.
There is scope for things to go wrong. Too much added thrust, badly timed and for no reason, can lead to a balloon and float effect... not ideal at all!
There is scope for things to go wrong. Too much added thrust, badly timed and for no reason, can lead to a balloon and float effect... not ideal at all!
Join Date: Jul 2011
Location: Unsettled
Posts: 60
Likes: 0
Received 0 Likes
on
0 Posts
A well-timed burst of thrust may make the difference between a firm touchdown and an over-G touchdown in difficult situations.
During regular landings there's usually no need for it.
During regular landings there's usually no need for it.
Join Date: Aug 2000
Posts: 1,501
Likes: 0
Received 0 Likes
on
0 Posts
There is another silly way to make good landings, always add 20 kts and float down the runway to a smooth landing.
Unless the weather dictates otherwise, idle landings will give you the shortest landing distance. That is all I care about. A smooth landing is not a good landing unless it is done at the correct spot at VRef -5 and at idle thrust.
In my career, I have only come across one pilot pushing the throttles up just before touch down. He would ALWAYS land at Vref + something and would ALWAYS use more runway than required.
Unless the weather dictates otherwise, idle landings will give you the shortest landing distance. That is all I care about. A smooth landing is not a good landing unless it is done at the correct spot at VRef -5 and at idle thrust.
In my career, I have only come across one pilot pushing the throttles up just before touch down. He would ALWAYS land at Vref + something and would ALWAYS use more runway than required.
Join Date: Jan 2006
Location: US
Posts: 2,205
Likes: 0
Received 0 Likes
on
0 Posts
Sloppy, lousy technique. Not uncommon on the 727. New FO's would be told the ususal B.S. "don't land at idle because the plane will fall out of the sky." 
Almost every 727 landing was at idle.
727 flaps 30 is less tricky than a 737NG with flaps 40. I'd estimate a 727 flaps 30 would be like landing a 737NG with flaps 35.
Almost every 727 landing was at idle.727 flaps 30 is less tricky than a 737NG with flaps 40. I'd estimate a 727 flaps 30 would be like landing a 737NG with flaps 35.
Psychophysiological entity
Isn't this all getting away from the point? In particular:
I would have thought the only justification for taking the engines through a sizable temperature cycle, and possibly making your field performance a little iffy, would be if the aircraft suddenly increases its sink rate and you had to do something.
There are aircraft where landing performance is based on throttles closed in the air. In a short field situation on jet transport aircraft, I personally liked to be a tad deeper into the drag curve and with stable commensurate power. It really did give the spool-up improvement needed to cope with nature's surprises. But, a late-state engine failure had to be built into one's cunning plan.
If you get a little slow, add the power. If it's a regular technique, it's purely sloppy.
I would have thought the only justification for taking the engines through a sizable temperature cycle, and possibly making your field performance a little iffy, would be if the aircraft suddenly increases its sink rate and you had to do something.
There are aircraft where landing performance is based on throttles closed in the air. In a short field situation on jet transport aircraft, I personally liked to be a tad deeper into the drag curve and with stable commensurate power. It really did give the spool-up improvement needed to cope with nature's surprises. But, a late-state engine failure had to be built into one's cunning plan.
Join Date: Oct 2007
Location: fort sheridan, il
Posts: 1,656
Likes: 0
Received 0 Likes
on
0 Posts
landing
the best advice for a smooth landing in a jet transport.
stable
flare
and then reduce the power
not reduce power and then flare.
j
ps... as I said and no one mentioned...spooling up just before flare means you will be ahead of the game in thrust reverse.
stable
flare
and then reduce the power
not reduce power and then flare.
j
ps... as I said and no one mentioned...spooling up just before flare means you will be ahead of the game in thrust reverse.
Guest
Join Date: Apr 2009
Location: On the Beach
Posts: 3,336
Likes: 0
Received 0 Likes
on
0 Posts
A 727 skillfully flown into the flare at V2+10 can usually have power reduced to idle prior to touchdown.
Unstable winds are a different matter, just as they are for most airline birds.
Unstable winds are a different matter, just as they are for most airline birds.
Guest
Join Date: Apr 2009
Location: On the Beach
Posts: 3,336
Likes: 0
Received 0 Likes
on
0 Posts
ps... as I said and no one mentioned...spooling up just before flare means you will be ahead of the game in thrust reverse.
Last edited by aterpster; 6th Nov 2012 at 01:12.
Thread Starter
Join Date: Oct 2006
Location: Ankh Morpork, DW
Posts: 652
Likes: 0
Received 0 Likes
on
0 Posts
If a modern jet engine with cascade-type engines only diverts part of the thrust for reverse, how can it be that adding thrust can be a good thing in the flare?
I'm all ears if someone's got some actual physics to back it up, but the same energy that is "improving" reverse thrust once you're on the ground has just pushed you 500' further down the runway.
Engines are more efficient at creating forward thrust than reverse.
I'm all ears if someone's got some actual physics to back it up, but the same energy that is "improving" reverse thrust once you're on the ground has just pushed you 500' further down the runway.
Engines are more efficient at creating forward thrust than reverse.
Guest
Join Date: Apr 2009
Location: On the Beach
Posts: 3,336
Likes: 0
Received 0 Likes
on
0 Posts
FlightPathOBN:
Do you have a reference for that?
Also, do you have an example of it in the U.S.?
exactly, and with the coded FP, the 2.8 GPA is becoming the standard...
Also, do you have an example of it in the U.S.?
Join Date: Apr 2008
Location: nowhere
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
Isn't that why some of these modern engines like the GE CF-6 have something called approach idle. Your engine is already spooled up for you. Seem to remember something called High Idle on some PT-6 equipped aircraft such as the King Air.
Last edited by JammedStab; 11th Dec 2012 at 21:57.
Join Date: Mar 2000
Location: canada
Posts: 147
Likes: 0
Received 0 Likes
on
0 Posts
IMHO it depends on the type of engine on the 'craft. Back in the old days on the 727, power was never put to idle until close to the landing. These were not "fan" engines. In today's big fan engines, where the fan produces 75% of the thrust, I would start to reduce power at 50 feet and be at idle by30 feet, raise the nose to 6 degrees on the horizon and kiss the ground softly. Couldn't do that on the 727.
T
T