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Adding Power Just Before Touchdown  
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17172 posts, RR: 66
Posted (5 years 4 months 3 weeks 1 day 2 hours ago) and read 6009 times:

After a wobbly landing 4 hours late with HK Express last night (well, early this morning), I was wondering about technique.

We were landing at HKG and it was rather gusty. About 20 seconds before touchdown, the plane rolled to the right rather noticeable. The pilot got her straight again. There were some more rolls, mostly to the right. We're not talking knife edge here, but enough to be readily noticeable by passengers. The pilot cut power and flared, and there was another roll. We were not a few feet (25-30?) from the ground with the aircraft rolled to the right. The pilot added power and we floated quite a distance down the runway at more or less level altitude. The plane then straightened and we touched down.

Yes, I do realize as a pax I don't have the correct sensory inputs to judge but I still want to ask if it is considered bad technique to add power just before touchdown and float down the runway while correcting? When would the situation warrant a go around?


"There are no stupid questions, but there are a lot of inquisitive idiots."
32 replies: All unread, showing first 25:
 
User currently offlineWILCO737 From Greenland, joined Jun 2004, 9118 posts, RR: 76
Reply 1, posted (5 years 4 months 3 weeks 1 day 1 hour ago) and read 6019 times:
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Quoting Starlionblue (Thread starter):
Yes, I do realize as a pax I don't have the correct sensory inputs to judge but I still want to ask if it is considered bad technique to add power just before touchdown and float down the runway while correcting?

I wouldn't say bad technique, but adding power adds some energy to the plane which you need to bleed away while braking. So the landing distance will increase and if you floated for a few seconds, then it will be even longer. As long as you are touching down in the touchdown zone, you are fine to land. We have a policy: if no toughdown in the touchdown zone a go around is mandatory.
Adding power to stop the airplane from further descending in this case and making some corrections is possible. As you have seen, they made it successfully. I can only tell from what I've learnt and it says: corrections that big at this time of the flight, then you better go around. I do NOT judge the pilots there as I wasn't there and don't know how big the correction was they needed to make. I am NOT saying it was unsafe or anything.
I did a go around once when we got hit by a gust at 20' and the power was at idle, we were drifting away from the centerline, I made a small correction to overcome the drift and gust. We could've landed, but it wouldn't be right on centerline, still with some slight drift and with bank. So I decided: Go around. So back into the air, safely making a short pattern and landing again.

What airplane were you on? The 737s have a pitch up tendency when adding power due to the underwing mounted engines. So if you add power at 20' the airplanes nose come up slightly and will stop the descent or decrease the descent. Some use this partly as a landing technique....

wilco737



It it's not Boeing, I am not going.
User currently offlineA320ajm From United Kingdom, joined May 2006, 547 posts, RR: 0
Reply 2, posted (5 years 4 months 3 weeks 19 hours ago) and read 5911 times:

I thought power was added before landing because an engine takes a longer amount of time to get from idle to enough power to perform a go around. If the engines have power just above idol, then the engines can be brough to full power a lot quicker for the go around.
Correct me if i am wrong

A320ajm



If the British Empire and its Commonwealth last for a thousand years, men will still say, 'This was their finest hour.'
User currently offlineB727LVR From United States of America, joined Jul 2008, 630 posts, RR: 0
Reply 3, posted (5 years 4 months 3 weeks 19 hours ago) and read 5908 times:

True, engines at a higher power setting will take less time to accelerate to full power, that could be a possibility.

However I do remember when installing engines on MD80's we would dome accel check from idle to max power and there was a max time limit they could be. I don't remember exactly what it was, but from idle to T.O. power doesn't take very long on a JT8.



I'm like a kid in a candy store when it comes to planes!
User currently offlineDAL7e7 From United States of America, joined Jun 2004, 357 posts, RR: 3
Reply 4, posted (5 years 4 months 3 weeks 19 hours ago) and read 5905 times:

I have a friend that flies 737's for CO and he told me that the trick to a smooth landing is to add a little power right before touchdown to, as WILCO said, slow the descent rate and smooth out the touchdown. The idle-TOGA thing is feasible though.

Quoting WILCO737 (Reply 1):
if no toughdown in the touchdown zone a go around is mandatory.

Toughdown... That accurately describes some landings I've been through.

IIRC, the AF 340 in YYZ (?) was hit by a wind burst and that's what lengthened the landing roll too much.

Thanks,
Trey



DAL7e7 is wondering... Do pilots take crash courses?
User currently offline9VSIO From United Kingdom, joined Dec 2006, 726 posts, RR: 2
Reply 5, posted (5 years 4 months 3 weeks 19 hours ago) and read 5901 times:
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Quoting A320ajm (Reply 2):

I was under the impression that drag flap (i.e. landing settings), in addition to creating more lift, also adds drag, thus requiring more thrust to keep the require rate of descent. Thus, the engines will already be slightly spooled up.

Thus, what you say is partly true, but not what Star is asking. If I'm not mistaken, most airliners will have a DH of around 200ft (in VMC)? Haven't done jets outside FTDs, but I use the "last second burst of power" if I need to cushion a suddenly large increase in the RoD in the vital moments of flare + float. Naturally, if there isn't much runway left, you just go around.



Me: (Lining up on final) I shall now select an aiming point. || Instructor: Well, I hope it's the runway...
User currently offlineEcuadorianMD11 From , joined Dec 1969, posts, RR:
Reply 6, posted (5 years 4 months 3 weeks 18 hours ago) and read 5886 times:



Quoting WILCO737 (Reply 1):
As long as you are touching down in the touchdown zone, you are fine to land

What zone is that to be exact please?
I know the beginning has like a mark (beginning of the runway), but how do they mark the end of this touchdown zone?
Or is this airline policy related?

Ecuadorian MD11.


User currently offlinePilotpip From United States of America, joined Sep 2003, 3152 posts, RR: 10
Reply 7, posted (5 years 4 months 3 weeks 18 hours ago) and read 5877 times:

Too many variables to say it's bad technique. Was it power to adjust for some shear and a sudden drop in airspeed accompanied by an increase in sink rate? Or did the plane float for a while?

If the touchdown was within the zone, fine. If it wasn't going to be, make a go around. Can't really say if I wasn't here.



DMI
User currently offlineB727LVR From United States of America, joined Jul 2008, 630 posts, RR: 0
Reply 8, posted (5 years 4 months 3 weeks 18 hours ago) and read 5868 times:



Quoting EcuadorianMD11 (Reply 6):
What zone is that to be exact please?
I know the beginning has like a mark (beginning of the runway), but how do they mark the end of this touchdown zone?
Or is this airline policy related?

If you were to look at the the runway looking from the end there are a series of white lines on either side of the center line that start with 3 lines, then down to 2, then to 1, this marks the landing area.


There is a fairly decent view of it here:

http://www.airliners.net/photo/15017...d=4468df1620e7e707881c4a7aae8c9b5f



I'm like a kid in a candy store when it comes to planes!
User currently offlineEcuadorianMD11 From , joined Dec 1969, posts, RR:
Reply 9, posted (5 years 4 months 3 weeks 17 hours ago) and read 5860 times:



Quoting B727LVR (Reply 8):
If you were to look at the the runway looking from the end there are a series of white lines on either side of the center line that start with 3 lines, then down to 2, then to 1, this marks the landing area.

There is a fairly decent view of it here:

Great pic, thanks!
I get "the picture".
What airport is that please?

Ecuadorian MD11.


User currently offlineB727LVR From United States of America, joined Jul 2008, 630 posts, RR: 0
Reply 10, posted (5 years 4 months 3 weeks 17 hours ago) and read 5855 times:



Quoting EcuadorianMD11 (Reply 9):
What airport is that please?

That is Los Angeles. It took me a while to find one that showed it well. Usually when I am just browsing I see them all the time or so it seems, but try and find one specfically... GOOD LUCK, lol.



I'm like a kid in a candy store when it comes to planes!
User currently offlineEcuadorianMD11 From , joined Dec 1969, posts, RR:
Reply 11, posted (5 years 4 months 3 weeks 16 hours ago) and read 5829 times:



Quoting B727LVR (Reply 10):
That is Los Angeles.

Okay, it looks like a TACA plane in the background, that´s why I was asking.
Don´t think you see them in L.A though.
The runway seems very sloped, or is it just my imagination?

Quoting B727LVR (Reply 10):
but try and find one specfically...

Yep, such is life.
The other day I was running around with a flat tire on my car, now you try to find a tire repair shop then.........
Needless to say, when I eventually had all 5 tires up to scratch, the rest of the trip I couldn´t keep up with counting the amount of tire maintenance shops I came across!! I think we all recognize that feeling............if you really need it...............nada!

We´re miles off topic...........sorry!!

Ecuadorian MD11.


User currently offlineInnocuousFox From United States of America, joined Dec 2003, 2805 posts, RR: 14
Reply 12, posted (5 years 4 months 3 weeks 15 hours ago) and read 5797 times:

Another thought is that it sounded like you had a bit of a crosswind. If that was the case, the pilot may have needed a few extra seconds of air time to line it up with the runway.


Dave Mark - Intrinsic Algorithm - Reducing the world to mathematical equations!
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17172 posts, RR: 66
Reply 13, posted (5 years 4 months 3 weeks 10 hours ago) and read 5690 times:

Well, I was glad there was no go around. With a 4 hour delay, landing at 0320 with 2 little kids I just wanted to go home.  Wink The landing was at HKG so I'm guessing plenty of runway available.

Quoting WILCO737 (Reply 1):
What airplane were you on? The 737s have a pitch up tendency when adding power due to the underwing mounted engines. So if you add power at 20' the airplanes nose come up slightly and will stop the descent or decrease the descent. Some use this partly as a landing technique....

737-800.

Quoting A320ajm (Reply 2):
I thought power was added before landing because an engine takes a longer amount of time to get from idle to enough power to perform a go around. If the engines have power just above idol, then the engines can be brough to full power a lot quicker for the go around.

As mentioned above, this is true, but the added power in this case was at the "last minute" just before touching.

Quoting Pilotpip (Reply 7):
Too many variables to say it's bad technique. Was it power to adjust for some shear and a sudden drop in airspeed accompanied by an increase in sink rate? Or did the plane float for a while?

As I felt it:
- Flare and power to idle.
- Sudden drop of right wing from a gust.
- Stop of descent.
- Slight hesitation and power increase. I guess spoolup took a moment.
- Float and roll to level.
- Power to idle and touchdown.

All this took only about 5-10 seconds I would guess.

Quoting Pilotpip (Reply 7):
Can't really say if I wasn't here.

And I was in the back so hard to tell for me too.  Wink I just wanted a bit of discussion on generalities. Good thread so far.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineFlighty From United States of America, joined Apr 2007, 8765 posts, RR: 3
Reply 14, posted (5 years 4 months 3 weeks 9 hours ago) and read 5660 times:

Putting on the logic hat, if you are hit by wind, and you are at idle power, you must add power to give yourself additional time to assess the situation. Otherwise you are exposing yourself to a landing in which you are no longer confident.

The pilot should be vigilant for the unlikely escalation of the event into bigger turbulence. You pause your descent by holding or climbing slightly, bumping the throttles to maintain airspeed. If everything is ok, you can resume the landing.


User currently offline411A From United States of America, joined Nov 2001, 1826 posts, RR: 8
Reply 15, posted (5 years 4 months 3 weeks 9 hours ago) and read 5655 times:

If one watches very carefully, the L1011, during a landing with automatic approach/land (autoland) engaged, together with engine autothrust, the throttles are very slightly advanced at 50 feet radio height, then retarded to idle at 5 feet radio height (and autothrust disconnected), just prior to touchdown.
Why?
That was the way the system was designed.
Results?
Extra smooth touchdown, nearly always.


User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 16, posted (5 years 4 months 3 weeks 9 hours ago) and read 5651 times:



Quoting DAL7e7 (Reply 4):
I have a friend that flies 737's for CO and he told me that the trick to a smooth landing is to add a little power right before touchdown

Yes that was the "gouge" in the 727 too but no

Quoting Flighty (Reply 14):
you must add power to give yourself additional time to assess the situation.

Not access the situation but to stop a drop . In gusty winds this isn't uncommon.


User currently offlineFlighty From United States of America, joined Apr 2007, 8765 posts, RR: 3
Reply 17, posted (5 years 4 months 3 weeks 8 hours ago) and read 5629 times:



Quoting CosmicCruiser (Reply 16):
Not access the situation but to stop a drop . In gusty winds this isn't uncommon.

Yeah, was thinking if you did not bump the throttles, you would not pause the drop. Then you could be headed for disaster if you are not fully sure of the situation down low. So the throttle add would be key. More power also widens your flight envelope if you have to do something drastic. But hey I am just a ground dweller, not a pilot.


User currently offlineTWAL1011727 From United States of America, joined Mar 2006, 637 posts, RR: 0
Reply 18, posted (5 years 3 months 2 weeks 13 hours ago) and read 4462 times:



Quoting EcuadorianMD11 (Reply 11):
Okay, it looks like a TACA plane in the background, that´s why I was asking.

Looks like a Kalitta air 747 to me.

Quoting EcuadorianMD11 (Reply 11):
The runway seems very sloped, or is it just my imagination?

Rwy 25L goes from 98 ft to 119 ft or a 0.03% rise (E to W) so it has a slope to it.
I think rwy 8R or 9L/9R at ATL is much more radical than any of the "level" rwys at LAX

KD


User currently offlineAaron747 From Japan, joined Aug 2003, 8289 posts, RR: 26
Reply 19, posted (5 years 3 months 2 weeks 12 hours ago) and read 4432 times:



Quoting Starlionblue (Thread starter):

Yes, I do realize as a pax I don't have the correct sensory inputs to judge but I still want to ask if it is considered bad technique to add power just before touchdown and float down the runway while correcting? When would the situation warrant a go around?

As many have stated, in just about any aircraft type, adding power is the only way to compensate for gusts or unwanted changes in attitude in the few seconds prior to touchdown provided that you're still in the zone. Check out this ANA 777 at NRT as an example:

http://www.youtube.com/watch?v=sJko7mAedBU

Quoting 411A (Reply 15):
Why?
That was the way the system was designed.
Results?
Extra smooth touchdown, nearly always.

Awesome - unfortunately very few of us will ever see this system in action.



If you need someone to blame / throw a rock in the air / you'll hit someone guilty
User currently offlineEssentialpowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 20, posted (5 years 3 months 2 weeks 11 hours ago) and read 4388 times:

On the long 737s (800s and 900s) adding power is the better option than increasing pitch attitudes above 6 degrees nose up or so. I think tail clearance in the 900s is 9.2 degrees.

As this is a forum discussing technique, I have been in a lot of RJs that are cross controlled like a C172 down final instead of being landed in a crab, and then flared high. Those factors increase the liklihood of a tail strike in a swept wing jet. In fact, some RJ operators have had tailstrikes on the T tailed RJs, which is unbelieveable...


User currently offlineThirtyEcho From United States of America, joined Dec 2001, 1659 posts, RR: 1
Reply 21, posted (5 years 3 months 2 weeks 9 hours ago) and read 4347 times:

Adding power right before touchdown has the effect of adding forward energy to a drift off the runway centerline due to a crosswind gust. Usually, a small, short burst of power will kill the drift and put the track right down the runway.

This is a common technique and is, in no way, unusual. Yes, the float will be slightly longer; very slightly.


User currently offlineEssentialpowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 22, posted (5 years 3 months 2 weeks 8 hours ago) and read 4337 times:



Quoting Essentialpowr (Reply 20):
On the long 737s (800s and 900s) adding power is the better option than increasing pitch attitudes above 6 degrees nose up or so.

And then tell the non flying pilot to select brakes from "3" to max", as a -900 at Vref 150 kts plus wind eats up a lot! of runway! (so im told)


User currently offlineThirtyEcho From United States of America, joined Dec 2001, 1659 posts, RR: 1
Reply 23, posted (5 years 3 months 2 weeks 3 hours ago) and read 4268 times:

This may, also, be the "roll it on" technique common to the B707 and B727 family. The power shot, precisely timed, slows the rate of descent and causes a small pitch up that gives you a "greaser" landing.

If you experienced this, I'd suspect a real grayhair at the controls.


User currently offlineMax Q From United States of America, joined May 2001, 4779 posts, RR: 19
Reply 24, posted (5 years 3 months 2 weeks 2 hours ago) and read 4264 times:



Quoting CosmicCruiser (Reply 16):


Quoting DAL7e7 (Reply 4):
I have a friend that flies 737's for CO and he told me that the trick to a smooth landing is to add a little power right before touchdown

Yes that was the "gouge" in the 727 too but no

This is one of the most common misconceptions and 'urban myths' in attaining a smooth touchdown.


Unless power is needed to arrest a high sink rate close to the ground.A proper flare and elimination of drift with the power at idle before touch down will always result in a better touchdown. This works as well in a 767 as it does in a 172.


Adding power or keeping power in actually 'drives' the Aircraft into the runway more forcefully. worst of all are the people I see trying this technique desperately hoping for a smooth touchdown as we float towards the end of the touchdown zone.


In this situation I tell them to take the power off or go around.


It's just poor Airmanship.



The best contribution to safety is a competent Pilot.
25 Aaron747 : True enough but you're talking about zero wind - quite different from what is being discussed elsewhere in the thread.
26 Zeke : Most probably due to some low level windshear, we have had a lot of that in the last month. For example the recently when I landed on runway 25 was,
27 Babybus : As far as I was aware, the 'touchdown zone' was an imaginary area taking up the first fifth of the runway. (I'm talking flt sim here) BA often seem t
28 CosmicCruiser : If you saw the figures on how much your stopping dist is increased for every extra 5 kts you carry you would see that you don't carry extra power and
29 David L : On the approach with gear down and flaps extended the engines will be at "quite a high setting" to maintain speed, which is handy for a go-around. Ho
30 CALPilot : All right, that's it... I call BS on this one. You have got to explain to me how adding power will correct lateral drift off center line? Funny I've
31 Max Q : I could not agree more, CalPilot hit's the nail on the head !
32 Aaron747 : With minor differences in handling and technique aside (bizarre wing designs not to be included in this discussion), the same holds true for all fixe
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