Landing speeds over Vmbe

[hawk37]

Let's say you've decided in an emergency to land your heavy jet, zero wind, where Vref will be well above your maximum brake energy speed. Is their an AFM procedure to follow? Aero brake until Vmbe, then brakes? Use rev thrust until Vmbe, then brakes? Use brakes first, then keep thrust reversers in use until stopped? What does Airbus/Boeing/SOPs say to do?

[Intruder]

It depends on the runway available... Specific procedures will vary with the airplane, but a general range may be:

If you're at Edwards AFB with effectively unlimited runway, use max reverse and no brakes until below 100 Kt or so.

If you have 12,000', figure out the landing distances for available autobrake settings, and use one that will stop you in 12,000'. Use max reverse as well, so you are not using the brakes alone to stop.

If you have less than that (i.e., not enough runway to stop "by the book"), use max reverse and max brakes, and get as slow as possible as soon as possible.

AFAIK, Boeing does NOT recommend aerodynamic braking in any foreseeable situation. Spoilers and brakes are less effective with the nose off the ground, and control is better with the nosewheel on the ground.

[gearpins]

Brake energy limits come into play during rejects and most a/c are designed to be able to t/o at max str limit wt and to reject (which is cerified without the use of rev any way) until complete stop using only brakes.(spoilers are allowed ofcourse).consequently in a situation as envisaged above the a/c is defenitely below max to wt. the energy that needs to be dissipated is shared by the revs additionally you normaly would have a longer dist to do it than in a reject.hope that helps:)

[Mad (Flt) Scientist]

Except that you only have to consider rejecting from max V1 (which may even be limited by Vmbe considerations) whereas the scenario suggested could have a higher touchdown speed (say flaps failed up, high airports only available).

[Intruder]

The scenario that most often comes up in training is a cargo fire just after takeoff. As a recent UPS fire illustrated, you may have NO time to get the airplane on the ground.

In the case of a 747 at max gross takeoff weight, it's a 90/270 and land opposite the T/O runway, unless the tailwind is too adverse. Then, a VERY short racetrack to final on the T/O runway.

With a -400 at LAX on one of the 25s, it's a likely good outcome. With a -200, the old steel brakes mean likely blown tires earlier, and more likely to run off the end.

Note that the max V1 reject has less runway to use than the max gross weight landing. However, the flaps won't come all the way down at approach speed (only to 25 due to automatic blowback), so that's yet another "gotcha"...

[mustafagander]

To contemplate landing above this limitation, there must be a very pressing need. Hence I would expect a pilot to just land and try to make the best of it. I would not try to be cute on approach - not below Vref +5 or additive required, stick to the customary 3* slope and put it on at the aiming point. After that, use all retarding devices available and see what happens at the far end of the runway. The usual maxim applies - it's better to go off the end at 50 Kts rather than fall out of the sky at 200 Kts.

Those B767 drivers here can imagine the scenario of a 185 T departure with flap asymmetry between 5 and 1 on retraction. After the additives the Vref can be rather impressive and few B767s can dump fuel.

[Alex Whittingham]

On the Handley Page Victor there was no reverse thrust, only a brake chute. If you didn't want to stream the chute the procedure was to land and wait and wait as the aeroplane very slowly reduced speed to VMBE, then brake as normal. The Vulcan used aerodynamic braking. On a modern aircraft I would suggest full reverse and continuous braking from VMBE down. In the cargo fire scenario would you have time to calculate VMBE?

[rhovsquared]

Vmbe is usually NOT a ldg factor [except in rare case such as a 757 coming in at MTOW as a result of an emergency] to a low Density alt:\ . I think the factor on ldg is 1.5% of the BE required for stopping at the highest Vref., and NO margins on the RTO at the Highest BF V1.
But as John Tullamarine warns all the time...Check you airplane's certifcation against the Applicable, CARs,JARs,FARs.



To The Tire Speed Limits And Beyond:} :} :}
rhov:)

[gearpins]

a flt ctrl problem will provide sufficient time to burn off and get the wt under control= for a smoke/fire/medical emer etc the land flaps(in most cases are available)= hence a combination of low/no flaps+over wt landing is a very remote possiblity:8 assume rtow is vmbe limited and you take off(using max v1) followed by an immediate return,remember v1 cannot be greater than vr which inturn cannt be greater than v2, which by the way is about 20% above vs. on the return vref for say the same wt is about 30% above vs. assume a stall speed of 180 kts so we are talking about absorbing the energy equvalent of 18 kts!!.with the luxury of reversers and longer r/w I dont see a problem

[rhovsquared]

Gearpins I was thinking about a very serious 'need to get down now!!!' type of thing...My point was one probably never will approach that Vmbe




Happy S-turns Along The Road:}
rhov:)

[Mad (Flt) Scientist]

assume rtow is vmbe limited and you take off(using max v1) followed by an immediate return,remember v1 cannot be greater than vr which inturn cannt be greater than v2, which by the way is about 20% above vs. on the return vref for say the same wt is about 30% above vs. assume a stall speed of 180 kts so we are talking about absorbing the energy equvalent of 18 kts

Actually, no, because the worst case is where V1 was restricted by Vmbe, not by Vr/V2.

If you were forced to have a low V1 due to V1max being restricted by Vmbe then it's possible that V1 might be 60-70% of V2, in which case your Vref will be substantially above the Vmbe.

The only good thing about such a scenario is that if you were able to accept such a low V1 then it's likely you have a very long runway, which will help when it comes time to land.

[rhovsquared]

from Geapins "vr which inturn cannt be greater than v2, which by the way is about 20% above vs"

V2[depending on the airplane it it's cert.] is either

1. 1.05 *Vmu if tail grounding limit or elevator power limited
2. 1.10*Vmu if not tail ground or elevator limited
3. The speed that allows the greater of either 1.1*Vmca or 1.2Vso to be achieved at the applicable screen height

though they are all fundementally related to Vso



Keep The Brown Down:}
rhov:)

[rhovsquared]

Whoops the above applies to Rotation Speeds:O
V2 =1.1 Vmca or 1.2 Vso...sorry




Keep It Straight:}
rhov:)

[gearpins]

I agree M F S "If you were forced to have a low V1 due to V1max being restricted by Vmbe then it's possible that V1 might be 60-70% of V2, in which case your Vref will be substantially above the Vmbe."
that certainly puts a crimp on the margins :bored: Another thought though the Vmbe limts are demonstrated with worn brakes (only 10% of normal efficiency;JAR/FAR):) .........got to run

[Intruder]

At max gross takeoff weight (377T), a 747-200 reaches Vmbe at about 130 Kt for a rejected takeoff. For a "normal" landing, it is about 190 Kt at max landing wt (285T) and 185 Kt at 300T. The chart I used doesn't go above 300T for landing, but the 130 Kt figure may be in the ballpark for a quick return after takeoff.

I agree that for a quick return at high gross weight, slow down NOW, and run off the runway at as low a speed as possible if that is inevitible.

[Mad (Flt) Scientist]

I'd say that the braking plan-of-action if you know you're going to exceed brake energy limits is rather type dependent. One type I was involved with a long time ago had no nosewheel steering, so a big concern if landing above brake limits was keeping enough brake efficiency to keep the aircraft straight once the rudder lost effectiveness. So I'd say if you have no NWS (either by design, MEL or due to failure) and have a Xwind you might have to try to keep some brakes to at least go off the end, not the side, of the runway.

if you do have NWS it would seem to make sense to use as much of the brakes as you can, but it still makes sense to delay if you can to maximise your aerodynamic braking contribution.

And I agree, with new brakes you're better off; but in today's economy, who thinks brakes aren't replaced at the last minute ....

[rhovsquared]

But, TO V1 is not limited at MTOW by Vmbe generally, Unless at high density altitude, so I think at lower DA's you may still have a margin even in an emergency scenario, I can't say where on a particular WAT curve...Also as was said, test were done with worn brakes and no RT so hopefully the holes don't line up like that:\




Happy Chandelles:}
rhov:)

[hawk37]

It depends on the runway available... Specific procedures will vary with the airplane,
As the original poster, I was hoping for an Airbus or Boeing specific procedure for a case when the pilot chooses to land over Vmbe.
Alex (Viktor aircraft RAF) implies land and wait for Vmbe was his procedure.
MFS doesn't give a procedure, I suspect none is specified for him.
Intruder suggest slow down NOW, and run off the runway at as low a speed as possible. Did you suggest there is an AFM landing distance for 747's when landing over Vmbe?

[Intruder]

No. I meant to suggest that you may not have a choice of landing runway/distance if you HAVE TO land that hot & heavy. If you don't HAVE TO, there will likely be enough time to get a phone patch with Dispatch (and Boeing Tech Group, if necessary) to help you make up your mind.

Please note the scenario i presented in my first post. That is the one where you can ONLY do a 90/270 and land, or a VERY short circuit to the longest/most wind advantaged runway. The only info you may have at hand is the limit gross weight for landing on that runway, which will give you an indication of how likely you are to run off the end, and/or a computer-calculated landing distance that will tell you the same thing.

[Spanner Turner]

Would it be possible to get the 'self loading freight' to put their feet out the bottom of the fuse and assist in braking? - just like the Flintsones. I'm a ground engineer and only once have I had the (mis)pleasure of having to change 16 wheels and brakes on a 747 - anything you blokes can do to avoid this is worth doing! In this scenario it quite often follows that an evacuation is set in motion and then I have to change 10-12 slide rafts as well. On second thoughts, I guess this is better than being thrown a shovel to dig a 200 ton aircraft out of the dirt! Go for the lot I say - bury your feet in the brake pedals, spoilers to full as you flair, and hold max reverse until stopped(engines surging or not). You guys do a fantastic job. :D

[rhovsquared]

Really, Vmbe is a ground speed limitation upon which the KE absorbed by the brakes is 1/2mV^2. but V1 V2 and V3 are airspeeds, so just because V2 is higher than Vmbe in airspeed, it may not correspond at lower dens. alt. to the ground speed limits, even though the IAS is greater.

On a TO limited by Tire [tyre:}] ground speed the speed near liftoff may be 190 Knots that is considerably higher than the IAS, say 150 KIAS, so at lower density altitudes you will have a V1 and GS more coincident with one another and the KE will be less.

You have no way of knowing, but generally, Vmbe is only at the limits of the TO wat curve [ 8000 or 10000ft] pressure altitude at ISA+15 or so.

You still may have quite a margin over the KE limits of the brakes despite the IAS for V2 or 'Vref' being higher than the TO V1, unless the TO was Vmbe limited in the first place...Also usually the MTOW is limited by the WAT curve to less than the sea level MTOW, and there are usually restrictions to the MTOW in the RTOW, so I still believe that for even a MTOW landing you should have at least some margin over Vmbe but you just can't know how much, especially if you're not right at the WAT limits.

Please tell me if there's fault in my logic, I'd really like to know???



TURBOCOMPRESORS OFF:}
rhov:)

[Mad (Flt) Scientist]

Let's assume a takeoff where you WERE limited by V1=Vmbe, at whatever altitude.

Let's also assume an 'old' aircraft where V2=1.2Vs and Vref=1.3Vs. (not sure I'll need this, to be honest)

Since you were able to get airborne from the runway concerned, you must have had enough runway to accomodate a lower-than-normal V1 and still achieve Vr/V2 at sensible proportions of the runway length.

We can also, perhaps somewhat with more difficulty, assume that the Vr-V2 speed spread is similar to the speed loss in the flare.

So, we know we have enough brake energy capacity to stop from V1.
And we know that we had enough runway to accelerate to V1, then either to (and past) Vr OEI, or to stop.

What we need to know is whether we can slow down from Vtouchdown to V1 in that same portion of the runway, which would leave us enough braking and pavement to come to a halt on tarmac.

1. Lets assume we were accel-stop limited.

http://img352.imageshack.us/img352/9056/vmbeos9.th.jpg (http://img352.imageshack.us/my.php?image=vmbeos9.jpg)


That means that the distance to accel from 0 to V1 (AEO) is all we have available to slow down from Vtouchdown to V1. I'd say it's likely that our AEO takeoff accel is rather greater than our no-brakes decel capability.
If we assume our decel is half the accel, then we get, for the distances to balance:

V1=sqrt(2/3)*Vtouchdown = 0.81Vtouchdown

Assuming we touchdown at 5-10knots below Vref, then we're looking at about 75% of Vref as the magic number for V1=Vmbe.

In other words, if your takeoff was accel-stop limited, and your V1 was ABOVE 75% of your Vref, then your accel to V1 took more distance than your coast/reverse thrust from touchdown to V1 will, and you have enough runway.
If, however, your V1 was below 75% of your Vref, you're probably SOL.

2. OK, Now for accel-go limited. (which probably a more likely case, I think)

This time we know the answer must be BETTER than the accel-stop case, because there's more runway in excess of the "stop" portion this time.

I can't right now see a simple relationship to use, since it depends too much on how close to balanced you were.

[skiesfull]

It is my understanding that any runway that a 747-400 can depart from at max. t/o weight, flaps 20, then it can return to that runway and successfully stop, on the runway.

[skiesfull]

To add to the above, in order to answer the original question, use normal flare and touchdown techniques with the use of max. braking (autobrakes or manual) and full reverse, until a safe stop is ensured.

[gearpins]

To add to M.F.S :- V1 must always be </= Vr it follows the max V1/Vr ratio=1. moreover it has been demonstrated that a V1 speed less than 84% of Vr renders the t/o distance too long and does not present any perfomace advantage. So its safe to assume: minimum V1/Vr ratio=0.84
this statement is with ref to the airbus family but the boeing or other figures would be in comparable range:)
to add to ρv^2ed :-Vmbe is one of the factors that limit V1 so in that sense V1 </= Vmbe.
the reference of 190kts i suspect has to do with tyre speed which by the way limits Vlof:)

[mustafagander]

AFAIK Hawk37 originally asked about an emergency return. Most of the time, except for simple EFATO, there is a Vref additive. As I previously posted, the B767 with a flap asymmetry between F5 and F1 on retraction would prove "interesting". An emergency generally means land the thing and do your best.

[Intruder]

rhovsquared wrote:
I still believe that for even a MTOW landing you should have at least some margin over Vmbe but you just can't know how much, especially if you're not right at the WAT limits.
While the 747-400 may be able to do that (per skiesfull), the 747-200 will not. Note that at max TOGW Vmbe is around 130 kt for the -200. Vref at that speed is 181, and approach speed at flaps 25 (flaps 30 won't extend due to load relief) is 191 kt at that weight. So, even with a generous "fudge factor," the Jurassic Jet will be difficult to stop on any normal runway. Waiting until 130 kt to start braking will likely cause an overrun on any "normal" runway (I don't have landing charts handy), even with reverse thrust.

[ShockWave]

Wow... that got a bit complicated.

In simple terms, cause thats all I can understand!

Vmbe is used to adjust your V1, t/off config etc for departure.

If you are returning to land after an emergency, you will have to do an overweight landing checklist on the AirBus, which will reduce your speed to Vls and provide max perf for the go around. If you can take off on it you can land on it, providing you don't have other failures that reduce your landing performance.
If you do, you will apply the landing distance factor provided for that failure to your landing dist required at your landing weight in config full.
If the runway is long enough you can land. You are not required to monitor Vmbe. However tire speed limits should be considered, especially at high elevation airports.

After landing I would use normal brakes and full reverse, reducing the brake use to ensure I used the full length of runway. Reverse thrust is not used in the Landing Dist required calc so it is a bonus and will allow you to avoid brake fires etc if available (hopefully).

[Intruder]

Which Airbus? Is what you say universal for the 300, 330, 340 (all series) as well as the 319/320/321? Energy is a LOT easier to manage with a lighter, slower airplane with carbon brakes. However, there are still a lot of airplanes out there that are heavier and faster than an A320, and that don't have carbon brakes...

[ShockWave]

I am refering to AB330-200, 340-300, 340-500, not sure about the 321 etc
If you're landing one of the above then the landing dist chart with or without factors will look after you.

[captainpaddy]

I don't know if I'm looking at this from too simple a direction but:

Takeoff from a 10,000 foot runway, abort from V1, leaves perhaps 4,000 feet to stop a heavy aeroplane. That will use an awful lot of energy.

Land back on the same runway, touchdown 1,000 feet past the threshold, leaves 9,000 feet to stop a slightly lighter aeroplane (more than twice as much room as above). That will obviously not require as much energy to be absorbed by the brakes.

The key I think is to do what almost every FCOM I've seen says, which is to modulate the use of brakes according to the runway remaining.

As mentioned earlier, the landing factor applied for every landing would allow significant extra distance to effect a more gradual reduction of speed. Provided the aircraft is placed on the ground early.

[hawk37]

MFS, it took me awhile but I was finally able to reproduce your calculations. I also assumed the deceleration to be one quarter the acceleration, and came up with:
V1 = sqrt(4/5) * Vtouchdown, and assuming Vref = 1.05 Vtouchdown then
V1 = .85 Vref is the magic number, where if V1 is below that then there may be problems.
I originally posted to inquire on Airbus/Boeing procedures when landing above Vmbe. It seems quite intriguing to me that there seem to be none published !!
Further, from the comments posted, there seems to be no way the crew is even aware that their landing may be Vmbe limited, ie that their Vref (or touchdown speed perhaps) is above brakes energy limit speed.
Airbus/Boeing operators concur?

[Clarence Oveur]

On the Airbus I fly, we have, in the Route Performance Manual, a max landing weight for the runway. It is often equal to Max structural TOW.

In case of malfunctions requiring an increment to Vref, the only checklist that makes reference to Vmbe is the 'No flaps no slats landing'.

In this case speed at touchdown is Vref +45, and landing distance mutiplied by 2. A graph is provided to determine max landing weight as limited by Max tire speed or brake energy (or LDA as the case may be).

I suppose it would be possible work backwards from the graph to determine a Vmbe for normal configuration. But judging from the numbers I doubt it would be worth the while.

http://i104.photobucket.com/albums/m194/Clarence_Oveur_2006/Image1.jpg

[Mad (Flt) Scientist]

OK, some numbers....

on the CRJ, V1 can be limited by brake energy : V1mbe the charts call it.

Assuming zero wind and zero slope, and at MTOW, it varies between 157 KIAS at sea level and 128 KIAS at 10000ft.

At the same weight, Vref is 154 KIAS

For reduced weights, Vref reduces by 5kts per 3500lbs; V1mbe increases by 4kts per 2200lbs.

So, at sea level, V1mbe at MTOW is greater than Vref, and there should be no problems.

At 10,000ft, V1mbe at MTOW is 26kts below Vref, and even allowing for some speed loss in the flare, its clear you couldn't apply brakes from touchdown with assurance. If we don't take any credit for speed loss in the flare, then there needs to be combined shift of 26kts in V1mbe-Vref.

Per 1000lbs, Vref reduces by 1.4kts, V1mbe increases by 1.9kts (approx) - so the net change is about 3.3kts per 1000lbs.

So at MTOW-8000lbs, Vref and V1mbe are equal at 10000ft - and MTOW-8000lbs is about MLW.

Therefore, there's never any real problem at low altitudes, or at higher altitudes if you stay below MLW. But if you're forced to do an immediate return at high altitude airports and are above MLW, you may be above Vmbe.

(Then the question would be: what's the WAT limited weight at such altitudes: is it above MLW or not?)

caveat: all numbers approximate and roughly read off charts, and DEFINITELY not official!

[rhovsquared]

Ah, some numbers to it those curves were helpful:ok:
I say the limiting situation will only be experienced by a lucky few:\



Of The Numbers:}
rhov:)

[Re-entry]

Hawk. To answer your original question, NO. Except , I suppose 'Emergency Landing Checklist'.
All the discourse about vmbe (whilst interesting) is irrelevant to your Q. Only max landing weight/ landing distance charts are defined for the scenario you describe. If MLW is exceeded, then the boeing AFM (747) offers the following:

OVERWEIGHT LANDING

Avoid using bank angles in excess of 30 deg when using normal landing flaps.

For flap 25 VREF landing speeds for weights above 317,000 kg refer to the performance manual.

CHECKLIST COMPLETE.

The reason for the limited info is to limit the manufacturer's and operator's liability in the (unlikely) event of such an immediate return, thus placing the main onus on the captain to prove he did the right thing. Bear in mind most emergency checklists contain the phrase 'land at nearest suitable airport'.

[Re-entry]

Once on the ground, normal stopping procedures. Get it on the pavement, speedbrakes out, full reverse, full brakes. Again no AFM guidance due possible legal ramifications. Blame the flight crew if you can.

[BizJetJock]

On the Cessna 650 series (Citation III, VI, and VII) the flapless landing checklist is interesting. At weights above 18000 (MLW 20000) you have an extra increment to the landing distance and the "Landing" section states:
3. Brakes.........Apply (Airspeed below 130 KIAS above 18000lbs)
Good game!:eek:

[Spanner Turner]

Let's say you've decided in an emergency to land your heavy jet, zero wind, where Vref will be well above your maximum brake energy speed. Is their an AFM procedure to follow? Aero brake until Vmbe, then brakes? Use rev thrust until Vmbe, then brakes? Use brakes first, then keep thrust reversers in use until stopped? What does Airbus/Boeing/SOPs say to do?

As the name suggests –I am an engineer rather than a driver. 747 is my forte and all below relates to the 100/200/300 747, so if I may add my two cents worth:-

I think the key word here is “EMERGENCY”. Can we also bear in mind that maximum braking can only take place during optimal conditions (i.e smooth runway surface, nice black asphalt, nil water/contamination which will all limit the intervention of the anti-skid system)
If you need to stop the plane in a non arthodox manner (emergency) - surely all deceleration devices must be used early and to their maximum – regardless of “Book Limits”

The manufacturer’s Max vmbe limit is determined as the limit at which, when this level of braking is applied, all components will maintain their integrity and be available for re-use. I.E – brakes will be fully functional after the appropriate cooldown period and all wheels will be able to be overhauled and re-used (obviously after tyre replacement due fuse plugs melting and tyres deflating) I’m thinking here of an RTO or max weight landing at the max weight figures/min runway lengths. You throw out the anchors, pull up in time, taxi or get towed back to the terminal, all your tyres deflate due fuse plug’s melting, everything cools down, I change 16 wheel assemblies, brakes cool off and due to everything being carried out within the “Max vmbe limit” the brakes are all A okay, we push you back and away you go! See below for what we have to accomplish whilst you wander into the terminal for a bit of Duty Free shopping whilst waiting!

D. High Energy Stop Conditional Inspection - Within DANGER Range
(1) Prepare for examination.
(a) Clear runway immediately after stop as tires will probably
deflate.
(b) Do not set parking brakes.
(c) Alert fire extinguishing equipment for hydraulic fluid,
grease or tyre fire.
W_A_R_N_I_N_G_: DO NOT APPROACH LANDING GEAR AREA FOR 1 HOUR AFTER
AIRPLANE HAS LANDED UNLESS ABSOLUTELY NECESSARY.
IF NECESSARY, AND SOME TYRES REMAIN INFLATED,
APPROACH AREA CAUTIOUSLY FROM FRONT OR REAR ONLY.
(d) After 1 hour, use fog or foam for cooling, or wait until
brake overheat warning light has extinguished.
W_A_R_N_I_N_G_: DO NOT SPRAY EXTINGUISHER OR COOLANT DIRECTLY ON
INFLATED TYRE OR WHEEL. EXPLOSION MAY RESULT.
(2) On axles where tyre has not deflated, no action is required.
(3) On axle where the tyre has deflated or the fuse plug released:
(a) Remove wheel and check for serviceability
(Ref 32-45-03/401 and 32-45-04/401).
(b) Remove brake and check for serviceability (Ref 32-41-15/401).
Remove antiskid transducer (Ref 32-42-09/401).
N_O_T_E_: Removal of axle sleeve (located under wheel) and axle
bushings (located under brake) is optional.
(4) On axles where one or both tires are deflated (melted or partially
melted wheel fuse plugs), remove both tire/ wheel assemblies and
axle spacer assemblies (Ref 32-45-01/401). Any wheels with fuses
melted should be removed, disassembled, and inspected for out of
round or loss of heat treat (Ref 32-45-03/601).
N_O_T_E_: Removal of the weight and balance transducer, the axle
sleeve (located under the wheel) or the axle bushings
(located under the brake) is optional.
(a) With the brake pressure off, it should be possible to easily
rotate each rotor (manually push the rotor at the drive key
slot with a tool). If only minor welding of the lining to
the rotor has occurred, it should be possible to easily
separate the surfaces by prying. Also, examine the heat stack
for evidence of cracked rotors and stators, loose lining cups,
or other evidence of overheat. Replace any brake with evidence
of heat damage leakage, or unsatisfactory operation (Ref
32-41-15/401).
QF (b) Refit serviceable wheel, tyre and brake (Ref 32-45-01/401
QF and 32-41-15/401).
(5) If a fire should occur, examine landing gear, adjacent structure,
and systems for heat damage.
2 . R_e_s_t_o_r_e_ _A_i_r_p_l_a_n_e_
A. Install components removed if serviceable. If not serviceable, install
replacement components.

Okay, all the above covers what happens when within “Max vmbe” – no lasting damage, just lots of work for me. Obviously the brakes are capable of pulling up the aircraft whilst heavier / shorter runway but we now go into the area of further damage / delay to the aircraft.

So, back to the original question of a ‘genuine’ emergency when you are over and above Max vmbe.

For a start, you’re in an emergency ( think now you have just rotated at MTOW and find out you have 2 kilo’s of semtex imbedded in your pilot’s seat and need to get on the ground and off the plane as it is timed to go off in 2 minutes). First thing out the window is any sort of “limits”. You perform a split ‘S’ turn, (fighter style), nail it on the deck just before the piano keys, before touchdown your feet are already pressed hard on the pedals(it’s okay – the anti-skid can cope with this), keeping your feet buried, you pull handfulls of reverser and speedbrake until the white dotted line in front of you has stopped rolling under the radome. You gracefully descend down the nearest escape slide, run off into the distance and whilst lighting a nice relaxing cigarette you look back and see your stricken bird.

Of course as a result of exceeding Max vmbe, here’s what you’ll see - the wheels will not be ‘deflating’ they will be ‘EXPLODING’, the tyres will be on fire and emitting massive plumes of black smoke, the brakes will have left trails of molten steel behind them, and what’s left of them will be glowing cherry red/orange, hydraulic fluid in the brakes will be vapourizing and burning and quite possibly the lower ends of the oleos will be ablaze/collapsing.

I have a video of this very event ( and for those of the 747 persuasion I have figures too) In 1974, as part of certification testing, Boeing took a 747-200(CF6-50 powered) to Edwards Airforce Base for a brake test(punishment). Aircraft weight was 823,000lbs(375,000kgs), Maximum braking was applied at 176 knots ground speed, spoilers were deployed but NIL reverse thrust, aircraft came to a complete stop at about the same time the tyres deflated, aircraft was able to TAXI under it’s own power to clear the active runway whilst the wheels exploded and brakes burnt themselves to oblivion. Nil fire retardant was applied for 5 minutes (to prove the ability of all on board having time to get out). Apart from the gear damage, there was extensive heat damage to the inboard trailing edge flaps which required replacement. The aircraft was able to be repaired within two days and continued with flight testing.

Guess what?? The test was considered a ‘failure’ due to insufficient energy absorbtion of the wheels and brakes(mainly wheel assemblies failing/exploding due to metal softening). Subsequently the wheels and brakes were further upgraded and the test repeated with even more impressive results!!

My point being, there is a lot of extra ability within your aircraft than what the “Tables” may say. Sure, as an engineer, I love you blokes to do your best to look after my babies and apply the limits when possible but if it’s yours and 350 other peoples necks on the line – just wreck the thing and get yourself off. All the engineer’s horses and all the engineers men will come along and put old ‘Aircraft’ together again.

I can just picture the scene now as Captain X arrives to see St Peter at the Pearly Gates.

“So Captain, I didn’t expect to see you here so early, what happened?”

“Well, I had to do a high weight emergency stop, and instead of hitting the anchors straight away, I waited until my speed dropped below that of Max vmbe, so my aircraft ran into the solid immovable object at the end of the runway. Bad news is that me and all the passengers perished, good news though is that the engineers pulled all of the wheels and brakes from the wreckage and they are still in service”

A new 747 can roll off the line in less than a month – it takes years and years to ‘roll’ one of you blokes off the production line. Don’t forget that you sit up the front, and will be the first to plough through the localizer antennae, grass, seawall, golf course(QF1), terminal building or whatever it is that lies at the end of the strip.

Other suggestions for pulling up an aircraft in unorthodox fashion,

Could you give it a handful of rudder/tiller and ground loop the old girl?
How about turning the anti-skid ‘OFF’ and letting the tyres flatspot, burst and then running the wheel rims/landing gear trucks/oleos into the runway? Me thinks that the co-efficient of friction of the tyres would be greater than the landing gear struts to the tarmac but it’s a thought! Main thing is to save your skin and that of the SLF.

If you’ve read this far – you could no doubt read War & Peace!! I think I’m done!