Overweight Landings

[777newbie]

Hi All,
In a large twin such as the 777, under what circumstances would you land overweight? To be more specific:
1) Engine fire after TKOF at MTOW. Fire is then extinguished. Dump or land overweight (all other factors favorable)?
2) Engine flame out at heavy weight. Land overweight just to save the fuel (all other factors favorable)?
3) Sick pax?
4) Do you have policies or recommendations from your airline?
Thanks in advance.

[gr8shandini]

I'm not an operator, but I would think that none of the scenarios you listed would justify landing above the published max landing weight. In doing so, you'd be risking structural damage possibly totalling a $100+ million aircraft. The only circumstances I could think of that would warrant such a risk is a fire that cannot be extinguished or the loss of a major lifting / control surface.

[NG_Kaptain]

All aircraft may land at max take off weight, there are different limitations applied. On the 340-500 we have an overweight landing checklist. It is not a dangerous exercise but certain criteria must be met, the FCOM has different max rate of descent on touch down for max landing weight and max takeoff weight. Certain conditions may preclude you from dumping fuel to max landing weight and we brief and those before takeoff. One is an uncontained fire and another is a person who needs medical attention urgently. To put the weights in perspective on very heavy flights on very long routes my airline does some ULR flights that after almost 14 hours when we reach our destination we are at max landing weight.

[DBate]

@ gr8shandini

I would think that none of the scenarios you listed would justify landing above the published max landing weight

I am sorry to say that, but you are quite mistaken. Here is an excerpt from our ops manual.


'...Overweight landings may be performed in all abnormal or emergency situations where according to the commanders discretion this course of action provides the same or a higher degree of safety than jettison fuel or continuation of flight.
Situations as serious illness of crew or other persons travelling on board which would require immediate medical attention also justify overweight landings...'

In doing so, you'd be risking structural damage possibly totalling a $100+ million aircraft.

Normal sink rate at touchdown averages 120 ft/min. Airplanes are usually certified with a sink rate of 360 ft/min at the structural limited TOW and with 600 ft/min at the maximum landing weight.
Structural problems will not arise, if sink rates at touchdown do not exceed 360 ft/min.

[Rainboe]

Shandini, with respect, but only in Pprune do you get non pilots jumping in with answers to flying questions of which they have no concept. You would have done better to keep out and let pilots answer! It's like an accountant watching a Doctor forum and stepping in with advice on obscure procedures! At least you gave a forewarning!
An active fire warning: even ceased, would have me landing as soon as poss.
Flame out: discuss with engineering possibly, but land.
Consider overweight go-around performance on one engine- not funny.
Sick passenger: depends on seriousness. If you start weighing the safety of 300 people against the health of 1, you are possibly already making a misjudgement.
No special guidance. Left to the experience and judgement of the pilot

[gr8shandini]

No worries. I'm always willing to admit when I'm wrong. The reduced sink rate limits didn't really cross my mind. I work in a certification environment so we're always working close to no kidding limits and much, much caution is taken.

[plain-plane]

Boeing have a very good article on this, in an old issue their Aeromagazine.
google: Boeing "Aero magazine", and "overweight landing"...

Just to make it too easy - Q3/07 - JT

Edit:
Thank you JT,

[Checkboard]

The article basically says that any problem that justifies a return to base will require far more engineering time than an overweight landing inspection - and, as stated, unless you really slam the landing, you won't damage the aircraft in the slightest. Epecially in these fuel tight days, the cost of dumping any significant amount of fuel FAR outweighs the cost of the inspection after returning!

[777newbie]

Thanks Guys,
Good Boeing article although I am thinking more about the actual situations that would make someone land overweight.
Rainboe, those were my thoughts also. In regard to a flameout, do you mean you would most likely land overweight? (I realise there are so many variables, it makes it difficult to make any blanket statements). Also would you consider not dumping to MLW in order to save the fuel? For example if the gear doesn't retract after TKOF and again all other factors are in your favour.
Thanks for all the thoughs.

PS; Checkboard - Of course some situations will need no engineering action apart from the overweight LDG inspection (eg; dying pax). The cost of fuel issue is more important these days. I wonder if any airlines are making recommendations to crew in regard to this?

[Rainboe]

In the absence of any indication of a fault, a simple flameout could be considered for relight. I would not do it as a matter of course. It is an extremely unusual occurence- I cannot say in years of operating jets I have ever actually heard of a simple flameout without any complications, so why should it happen? I would look at the operating envelope/icing conditions and also discuss with company engineers before relighting. But there is not a lot of time to waste, as when a twin is on one, the instruction is 'land at the nearest suitable airfield'. Therefore, don't stooge around for 50 minutes dumping. Get it down- you should not leave 200 people depending on one engine. Gear problems......you are not going anywhere, unless it's a short hop to a repair station, yet not an emergency requiring an immediate landing. You have time to think about it!

[fourgolds]

The Boeing Aeromagazine article is a good one on the subject.

I think the answer is very situation specific. mr Boeing says if you take off you can land ( just check for contaminated conditions though ). So if all hell is breaking loose you should be able to get it back safely stopped on the runway . However you may well blow out some tires and risk a brake fire ( at very high weights). Remember on the 777 the landing distance given is for max manual braking , which on a very overweight aircraft equates to meltzone ( dammaged undercarriage at least)in most cases.

I think the various situations you ask about are case specific. If the engine just flamed out and the other was performing normally I would jettison if it was required to return. If it had a fire , severe dammage ( extinguished) I would need to evaluate the dammage and structural/systems integrity before deciding. eg if we had a "serious" fire that is now out . I would land ( as the wing could now have integrity issues). So there is no clear answer.

I feel the harder decision is the sick passenger example. You take off max take off weight. Just after take off , you are advised of a passenger who is gravely ill. Will you now go back and land ( blowing out tires , hot brakes etc) to save one life.?

This is a tough call , I would use all the resources avail to help mitigate my decision ( and back me up at the subsequent board). I would make pretty sure that I had the medical accountability given to the medical staff ( in my company Medilink). I would explain to them and the company the ramifications of an immediate return. If they felt the person required immediate help fullstop, then I would land. Its easier justifying the loss of a few tyres than the loss of life. But if they were wishy washy about the condition I would push then for tha wishy washy condition statement , that would protect me in court and delay while we get the weight down.
Off course if there is some other resaon that jeopardizes the safety of the aircraft I would not compromise all for one.

Good luck with the decision making , GREY GREY GREY