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B777 single engine overweight landing question.

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B777 single engine overweight landing question.

Old 7th Mar 2019, 21:14
  #41 (permalink)  

Only half a speed-brake
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Originally Posted by ASRAAMTOO View Post
So to summarise, last week you are not landing overweight, this week you are.
The problem there lies with the company policy, associated training and its application.

It is 2019, the manufacturers are ready to help and put all their knowledge and customers' operating wisdom into the guidelines already. If those are seen as vague it means getting more specific had drawbacks here and there that would be too impractical to deal with or undesirably restrictive. It is easy to to create policies for the calculated, but when the unforeseen arrives one could find himself missing tools needed for the job very easily.

For instance the article wiggy linked has all you need.
- staying inside the Operational Landing Limit {which is never higher than the structural) is a legal requirement
- there is no technical aspect preventing an overweigt landing. Extensive description how and why.
- as long as the landing performance works with standard landing flap (on the runway one just departed from it always does, by a factor 2,5 ish).

My short? The A/C is built per certification requirements to enable an overweight landing at MTOW. You foul nothing doing so, and reasoning around the legal aspect is the single remaining task.

If you need a more definite clause, inevitably the discussion stucks over the meanings of "needed", "ensure safety" "preferable" or similar. Terms that are subjective constructs and have no measurable meaning to begin with. Watch the other distinguished posters draw swords over "not recommended" and "non recommended". Both probably native English speakers and pilots.

FlightDetent is offline  
Old 8th Mar 2019, 01:35
  #42 (permalink)  
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As per our Ops manual, Eng failure is a MAY DAY call. The list also includes many others scenarios as well.
as per my understanding uttering MAYDAY Means now you are also time critical which would defeat the very purpose of the call if someone opted to jettison.

the only reason one would probably decide to reduce a/c weight either to Max landing or higher just enough to ensure adequate landing dist margins are avail at the Land ASAP airport.

I rather not get into back stage factors as to why the ops manual says MAYDAY for single engine, or climb gradient requirements of the approach you make or like some people say be extra safe and think of the tyres etc...

one thing would be certain that overweight landing and other relevant checklists will all be carried out in time before landing.
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Old 8th Mar 2019, 21:14
  #43 (permalink)  
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On the subject of MAYDAY/PANPANPAN or whatever you like ,remember one of the main reasons for giving this call as early as possible after the event. Its all about the biggest threat,and it's probably not to you!
What have you left on the runway,on that dark and dirty night,that the next departure may well hoover up!
Yaw String is offline  
Old 7th Apr 2019, 11:48
  #44 (permalink)  
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Both ways will probably have a safe outcome, I agree.
There are some companies that will support either way and not ever second guess you......there are also some companies that will say bring it back, land overweight, but God forbid you have a few fuse plugs melt, have hot brakes get welded to the axle or anything and it will all be "your fault"and you will be out the door..... Vapp at 345 tons is 201 kts, so good chance things will heat.
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Old 7th Apr 2019, 12:24
  #45 (permalink)  

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What's the V2 with takeoff flap, casa? Do tell.
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Old 7th Apr 2019, 19:37
  #46 (permalink)  
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Depends on number of factors but around 187?
have seen several RTOs that have caused damage due to hot brakes...
quite likely that doing flaps 20 approach due to 1 engine inop you will be over 200 kts. Hypothetically possible to exceed max tire speed of 204- which may warrant changing all tires, definitely be in the fuse plug melt zone, so strong possibility expensive repairs required...... “if” that happens I would wager many companies might say why didn’t you dump fuel????
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Old 8th Apr 2019, 02:10
  #47 (permalink)  

Only half a speed-brake
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That really is a lot of E(k), in high PA environment.
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Old 9th Apr 2019, 08:03
  #48 (permalink)  
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A bunch of incorrect information on certification requirements has been written in this thread.

The regulation that determines whether a jettison system is required is 14 CFR 25.1001(a). It has nothing to do with the relationship between max takeoff weight and max landing weight. The requirement for a jettison system is instead based on climb capability at a weight equal to max takeoff weight minus the weight of fuel necessary for a 15 minute flight consisting of a takeoff and return to land. If the climb gradient requirements of sections 25.119 (all engine climb in the landing configuration flaps down gear down) and 25.121(d) (engine out climb in the approach configuration flaps down gear up) cannot be met at this weight, then a jettison system is required by 25.1001(a).

The flow performance of the jettison system, if required by 25.1001(a), is required by 25.1001(b) to be able to get the airplane within 15 additional minutes to a weight that allows the airplane to meet the climb gradient requirements of 25,119 and 25.121(d).

The braking system regulation, section 25.735, sets the energy absorption capability requirements for the brakes. Landing at max landing weight at anticipated speeds must be withstood repeatedly as normal operation with no damage other than normal wear. Landing at max takeoff weight must be withstood without hazard, but parts can be destroyed or require inspection/maintenance. The structural regulations (25.473) set the landing loads that must be met by setting descent rates that must be accommodated as limit loads at max takeoff weight (6 feet per second descent rate at touchdown) and at max landing weight (10 feet per second descent rate at touchdown). A design can be limited by the braking and structural regulations to a maximum landing weight that is significantly less than the maximum takeoff weight, and whether or not a jettison system is required would have nothing to do with this. It's all design choice - how strong do you want to build your gear and brakes, and what climb performance do you want to provide.

Of course, performance information (climb gradient and runway distance) for landings in excess of the maximum landing weight up to the max takeoff weight is required to be provided in the AFM by 25.1587(b)(3).

So yes, as most of you pilots already know, you can theoretically land safely above the maximum landing weight, but you are going to at least have some inspections required afterward, and worst case could blow the tires and damage the brakes and wheels. I am not qualified to speak about the judgment of whether you should do this in a real world situation.
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