PDA

View Full Version : 737 All flaps up landing -a question on airmanship


Tee Emm
1st Apr 2010, 13:20
With regard to use of autobrake on MAX if perchance you are conducting an all flaps up approach and landing on a limiting runway length.

With a typical VREF of 190 knots at max structural landing weight in the 737 Classic, the use of auto-brake to MAX would possibly (?) increase the chances of a tyre blow-out shortly after the main wheels touch down. My guess is the risk of that happening should be considered during the pre-approach briefing. If that happened on the limited length runway above, the chances of an over-run would be quite high.

Prompt application of full reverse thrust at the high touch-down speed of around 185 knots would be extremely effective as we know that reverse thrust is more effective at high speeds - hence the Boeing FCTM recommendation that "the importance of establishing the desired reverse thrust level as soon as possible cannot be overemphasised."

Assuming the touchdown is at the correct speed and at the correct spot, then rapid application of full reverse will quickly reduce the airspeed at a faster rate than a normal landing flap reverse application. (lower speed - less efficient reverse).
Obviously brakes will have to be applied shortly after touch down on the limiting length runway - but the question is at what speed to avoid the risk of tyre blow-out.

We know that manual braking gives greater stopping capability than any of the auto-brake settings, including MAX. In fact on a limiting length runway, with an all flaps up landing with MAX autobrake selected, simulator experience has shown that over-riding the MAX autobrake into max manual braking is needed to stop the aircraft by the end of the runway.

The pilot is faced with two options as I see it. Use MAX autobrake selection in conjunction with rapid selection of full reverse and later transition to max manual braking to stop in time. Risk of tyre blow-out due very high speed touchdown and subsequent degradation of braking capability.

Or - autobrake selector off for landing - rapid selection of reverse immediately after touch down which - in conjunction with spoilers which are also effective at high speed then soon after manual braking up to maximum. The aim to reduce the risk of tyre blow-out caused by MAX autobrake on touchdown which would certainly result in an over-run - versus - a less chance of tyre blow-out by not braking until later when heavy manual braking in conjunction with full reverse makes succees highly dependant on when maximum manual braking is initiated?

At the subsequent Court of Inquiry (as my Wing Commnander would say) would the pilot run the risk of censure if he opted to use Max Autobrake for landing and subsequently blew a tyre by doing so and over-ran the runway? Or would he risk censure if he left maximum manual braking too late and over-ran because he was concerned that a blown tyre on touchdown posed the greatest danger?

Discuss the airmanship aspects of either decision..

kenparry
1st Apr 2010, 14:04
Why do you think max autobrake will give you a tyre blow-out? I think your fixation on this is flawed. An aircraft on which this selection would cause that result would IMHO not be certificated. You should perhaps be more concerned about brake energy limits, and the info on that is presented in the FM.

If by "blow-out" you mean the blowing of tyre fuse plugs by the spread of heat from the brakes, that would happen some minutes after landing, and not during the landing roll.

Tee Emm
1st Apr 2010, 14:39
If by "blow-out" you mean the blowing of tyre fuse plugs by the spread of heat from the brakes, that would happen some minutes after landing, and not during the landing roll

Thank you for that information. Believe it or not I was quite aware of that. Fortunately an all flaps up landing on a limiting runway length is an extremely rare event and most pilots would never hear about such an event unless it happened within their own sphere of operations.

While the autobraking system is certified to cope with high speed aborts within normal weight range I wonder how many high speed aborts also result in a blown tyres somewhere during the RTO braking? Answer - I don't know because figures are hard to find or are not specifically recorded for all to study. But, if in fact tyres have been known to fail during a high speed RTO, then I suggest they could also risk failing at the extremely high touch down speeds associated with an all flaps up landing. I can produce no hard facts in this discussion nor did I pretend to know any. The subject was meant to promote discussion from which I could learn something from the highly experienced people that frequent Tech Log.

kenparry
1st Apr 2010, 17:29
No need to get shirty. My reply was based on somewhat more than 20 years in the front seats of various Boeings, including the B737.

Intruder
1st Apr 2010, 17:45
You'd have to take a look at the brake energy charts to see if the kinetic energy to be dissipated at landing weight and no flaps is more than that at max T/O weight and normal T/O flaps, assuming some nominal max V1. While it is likely that the brake energy limit would be exceeded at max landing weight, it should not be so at light weights. Using max reversers would also help significantly.

Also, the antiskid should prevent wheel lockup and the resultant blown tires, though fuse plugs would likely give way later.

BOAC
1st Apr 2010, 17:56
.........and then, of course, unless you HAVE to land on a limiting runway.....................

Flight Detent
2nd Apr 2010, 03:19
I think I understand your concern...

In my experience it's sometimes difficult to concentrate on both selecting max reverse AND effectively applying max manual braking at the same time.

As a result, might a selection of medium autobrakes be better, which as you know will start as soon as wheelspin is detected (as it does with all brake selections), whilst your efforts to get maximum reverse are in train.
When max reverse is successfully in place, then you might divert your attention to overriding the autobrakes (or manually reselecting to MAX), manually to get the desired effect.
Remember with auto brakes, the target decel is augmented by the reverse thrust effect, which is not the case with manual braking!

I suggest not even considering the eventual effects of the wheel fuse plugs, that's something for much later, after you've stopped and taxied off the active!

Cheers...FD...:)

b737NGyyc
2nd Apr 2010, 06:19
From my FCOM performance section the landing distance required for an all flaps up landing at max landing weight of 129,200 lbs is just a hair over 4000 feet. This assumes a VREF of VREF40+55 knots, Sea Level and max manual braking and max reverse thrust. This would probably result in the fuse plugs melting after landing so if you had extra runway available and stopping was assured I would probably ease up on the braking effort and trade runway length off against braking required to safely stop. There is little to be gained by screeching to a stop in 4000 feet of a 10,000 foot runway and melting the fuse plugs.

If you are considering an all flaps up landing on a runway shorter than that IHMO you had better be on fire too.

I would have a hard time justifying a normal flap 40 Autobrake 3 landing on a runway that short. In fact the landing distance required in this config on a dry runway is 4600 feet.

There are very few airports that we operate B737s into with runways this short. In fact most airport's shortest runway is double this length.

Wizofoz
2nd Apr 2010, 07:56
I wonder how many high speed aborts also result in a blown tyres somewhere during the RTO braking?

Pretty much none.

There is plenty of data on this. It is a certification requirement that RTO can be carried out at the maximum allowable V1 without stryuctural damage, and that includes "Exploding" tires.

Hava a look on Utube at some of the RTO testing Airbus and Boeing do on much heavier aircraft that the 737. You will get brake fires before you get tire faiures.

Max Autobrake is still less braking than RTO, so I do not see why there should be any risk of "Blown Tires" implied by it's use, even at the high speeds you mention.

A37575
2nd Apr 2010, 12:50
No need to get shirty. My reply was based on somewhat more than 20 years in the front seats of various Boeings, including the B737.

No need to start a pissing contest here..

LLuke
2nd Apr 2010, 22:55
I wouldn't worry about the tires.

I'd expect most heat to be coming from the brakes. Transfer of energy to the tires will take some time. By the time the fuses pop, you'll standing still already.

SCD you can opt for other solutions, but it will require a lot of explaining when it doesn't work out.

timzsta
3rd Apr 2010, 07:57
There are two of you up there. Perhaps one could apply reverse thrust (PNF?) and one override the brakes (PF?). Just a thought from someone who operates single crew....

frontlefthamster
3rd Apr 2010, 09:57
Two very good reasons to use MAX:

1. If you don't, and you go off the end, you'll carry a heavier can;
2. Achieving an accurate touchdown all flaps up is not easy. The handling is very different, and line pilots rehearsing in the simulator often overcook the flare and float quite badly. Reasons for this are the lighter stick force at high speed clean, and the powerful visual cues from the high ground speed. (Tip: if you have to do this for real, aim for a very slight nose up pitch input, and ask your P2 to guard the control column from more than about an inch of rearward motion in the flare).

Very few pilots get to land all flaps up, and the odds against having to do it on a limiting runway are so great as to suggest that there is no real reason to ponder too much on this particular topic.

The hamster's list of valid reasons not to use MAX:

A37575
3rd Apr 2010, 14:04
ask your P2 to guard the control column from more than about an inch of rearward motion in the flare).


Oh lovely thought...two pilots on the same control one pulling the other trying to stop the pulling is really asking for trouble.

Boeing man
3rd Apr 2010, 15:03
Hi just a reminder the landing distance given in QRH will be unfactored depending on airline proceedures you may have to doudle this dist or correct it by 80 percent so long runway required so alot more than 4000 feet

FlyingOfficerKite
3rd Apr 2010, 16:57
'Guarding' is not 'holding' so why the conflict between the pilots?

I don't think that is what was implied at all?

KR

FOK

usanxb
13th Jun 2011, 02:11
I concur with the original posting in conjunction with the Boeing recommendation:

"The importance of establishing the desired reverse thrust level as soon as possible cannot be overemphasized." This worked successfully only several weeks ago on an 8600 foot strip.

This recommendation seems to over-ride whatever the pilot in command decides to do regarding either using, or not using, auto-brake facility.

Full or partial flaps up landings are not as rare as imagined. Nor is the possibility of an asymmetric landing due to in flight engine out condition.

Does anybody have any experience of the combination of these two events on a restricted strip?

N

ps. I guess it's best tested on a somewhat longer strip for those lucky test pilots.

STBYRUD
13th Jun 2011, 09:41
Hmm, no actual experience with an event like that, but I would make sure I touch down with minimum speed as early as possible, yank the reversers full open and use as much manual braking as necessary - the problem I see with autobrake MAX is that even this commands a certain preset deceleration (unlike RTO) that might in that case not be enough - and if reverse thrust will cause you to exceed that preset deceleration autobrake will modulate the brakes, not really what you want if you really need to stop on a dime.

NigelOnDraft
13th Jun 2011, 09:48
Fortunately never had to fly the 737 ;)

But in generic terms, and your request re 'Airmanship'. I would suggest that your efforts are best directed at:

Finding the longest into wind runway
Planning the approach and touchdown
Most importantly, detailing the GA (depending on other failures) criteria, and up to what point it can be called, and ensure NHP is prepared to call it - without further failures, I might even "plan" on a "low" GA, and only land if we are both 100% happy.
Most jets, Flapless, will need to come in on a 2.5 slope for speed control, and hardly flared (as above). A good 1.5g+ landing * (which from the back of a 737 seems quite easy to achieve even with flaps :rolleyes: ) will do wonders to wipe off some energy.Get the (ground) speed and point of touchdown right, and the issue of stopping will be relatively minor. Get them "wrong" and it will be academic.

NoD

* Please don't comment on this "maybe requiring a heavy landing check". Even if it does, it will take a fraction of the time sorting the flap problem out, and if you can achieve a "heavy landing" flapless you have done better than I have done/seen in various jets flapless :{

rudderrudderrat
13th Jun 2011, 10:41
Hi NoD,
Fortunately never had to fly the 737 pity - Affectionately known as FLUF.
Most jets, Flapless, will need to come in on a 2.5 slope for speed control
How do you do that at LHR or LGW with a 3 deg glide slope?

Centaurus
13th Jun 2011, 12:38
But in generic terms, and your request re 'Airmanship'. I would suggest that your efforts are best directed at:

Finding the longest into wind runway


That is true of course. But the original post stated clearly that the landing was on a limiting length (for the all flaps up case). All the rest of the stuff you added is superfluous. Sorry about that but that's the budding lawyer in me:ok:

cosmo kramer
13th Jun 2011, 14:41
Boeing already answered your questions for you:

FCTM, Chapter 8 non-normal operation, All flaps up landing:
Use of autobrakes is recommended. Autobrake setting should be consistent with runway length. Use manual braking if deceleration is not suitable for the desired stopping distance.

Immediate initiation of reverse thrust at main gear touchdown (reverse thrust is more effective at high speeds) and full reverse thrust allows the autobrake system to reduce brake pressure to the minimum level. Less than maximum reverse thrust increases brake energy requirements and may result in excessive brake temperatures.

In other words Boeing absolutely do not recommend that you do not use the wheel brakes upon touchdown (either max manually or with an appropriate autobrake setting for the available runway length). With that in mind I think there is a much greater likelihood that you will blow a tire with manual braking at an approach speed of 180ish kts (NG) than with max auto.

Personally I would choose max auto, to assure a decent stopping power immediately at touchdown (certainly faster application that with manual) and that braking is in progress in the delay time before the reversers deploy.

When the reversers take effect the brake pressure will reduce hence the chance of a blow out will reduce. At this point I would switch to manual braking if needed.

Not using the autobrake at touchdown would be counter productive and against Boeing's recommendations.

Further...
FCTM, chapter 6 Landing roll, wheel brakes:
Although immediate braking is desired, manual braking techniques normally involve a four to five second delay between main gear touchdown and brake pedal application even when actual conditions reflect the need for a more rapid initiation of braking. This delayed braking can result in the loss of 800 to 1,000 feet of runway. Directional control requirements for crosswind conditions and low visibility may further increase the delays. Distractions arising from a malfunctioning reverser system can also result in delayed manual braking application.
...supports the reasoning to use autobrakes initially and later switching to manual if needed.


From an airmanship perspective, what should be your greatest fear with a flapless landing on a restrictive runway (say less than 2000 meters)?

1) A very likely overrun into the landing lights, localizer antennas etc. due to insufficient braking?

2) A remote possibility of blow out at some point in the landing roll which may not certainly degrade your braking performance to the point that it will cause an overrun.

irishpilot1990
13th Jun 2011, 22:37
No need to get shirty. My reply was based on somewhat more than 20 years in the front seats of various Boeings, including the B737.

How many flaps up landings did you do on limited runways? Or how many tyres have your burst with max manual braking?:E:E:E

P.S no need for hernia's I am just messing:ok:

Lonewolf_50
13th Jun 2011, 23:11
Question for the OP, and those who fly the 737: (Nigel, your points are good airmanship points, please bear with me)

IF you have to do a flaps up landing because you don't have a choice
AND your runway choices are limited to "short" per the OP,

is there not a consideration to get light (fuel dump) before you begin your approach to reduce landing distance required? :confused:

OR

are those x thousand pounds, or not, of marginal influence so as not to be worth adding into your pre-landing plan for a flaps up landing? "Get light" seems to me one of the variables you can control, in modest measaure.

(Yes, I realize enviro issues, and an accountant's "What, you threw away perfectly good fuel?" issues arise, but I am asking to understand the airmanship question ... )

Denti
14th Jun 2011, 04:18
No fuel dumping possible, but extending the landing gear and speedbrakes while flying a holding burns off fuel fast. However, consider a possible go-around due to uncommon approach attitude and speed and keep enough fuel for that.