747 Take-Off Run

[carl josef]

Hi all,

what is the approximate take-off run of the Boeing 747-400 at MTOW? (I do not mean take-off distance)

Beside personal experience I would appreciate written sources for that information ( I have manuals for the 757 and DC-10 for example, and do not find this sort of information there).

Kind Regards
Carl

[18-Wheeler]

If you don't mean distance, I guess you mean time ... ?

'Bout 45 seconds or so.

[carl josef]

I mean take-off run as distance to the last point when main wheels stay on the ground and not take-off distance (TOD), which as I understand is the distance to the point when the plane has height of 35 ft.

Carl

[Flight Safety]

This is a Boeing website link that may have the information you're looking for.

Boeing 747 performance information (http://www.boeing.com/assocproducts/aircompat/747.htm)

Scroll down to the 747-400 section, then click on the "3.0 Airplane Performance" link. Takeoff and landing distances, as well as other performance data, are contained in the .pdf document. You will also see that performance data is available for other versions of the 747 as well.

[carl josef]

thank You very much!

But they give FAA runway length and not the ground run distance I´m looking for.


Carl

[john_tullamarine]

Does not the AFM include some takeoff run charts ? ... which will give you the information you are after ...

[18-Wheeler]

If you're happy with a rough guess, I'd ay about 200 metres shorter would be about right. Maybe a touch less .... ?

[john_tullamarine]

.. going to depend on the extent of clearway scheduled .. but, generally, a lot more than 200 m.

[mutt]

Please put me out of my misery...... why do you want this particular distance?


Mutt. :)

[carl josef]

mutt,

I like to know if Microsoft´s FS2002 PC Flight Simulator does it right.

Deficiencies in that programm always make me learn more of real-life aerodynamics and flight-mechanics.

So I´m now thinking of the farther issue: What is the absolute minimum rotation and lift-off speed, not including any safety margins at MTOW and Standard conditions.

Sorry, maybe I should have asked this question in the Flight Testing forum.

Is there any objection to put it there too ?

Thanks for all replies
Carl

[18-Wheeler]

FWIW in the simulator I've practiced getting the 747 off the ground in much less than the normal ground roll. At about 270 tonnes, I rotated at ~90kts, pull it off the ground and held ~110kts. The stick shaker was rattling away madly, as there was airframe buffeting, but the plane flew.
The ground roll was perhaps 1,100', no more.

[mutt]

If i was to tell you that the answer was 8,753 feet, how would you compare this to the FS2002 distance?

I would be very surprised if you find any airline pilots who have actually tested VMU speeds or MinVR,

Mutt.

[18-Wheeler]

Be surprised then.
The reason I was taught it is because the airline that ran the sim had at least two incidences where cars or planes had taxied out in front of them on the take-off roll, so they were teaching their pilots how to get the thing off the ground in a hurry.
The airline I was flying for at the time hired the sims off the other airline and we were swapping over to their procedures, so we did a little extra training on top of that.

[mutt]

I knew that I should have added the line..in the aircraft……….


Cheers

Mutt. :):):)

[Fright Level]

18 wheeler posed a worrying thought. You either have a V1 or you don't. I have never heard of a conditional V1 (ie, we'll stop except if it's a vehicle ahead when we'll rotate early).

I know the arguments between stopping and certainly hitting an obstacle (at a lower speed and decelerating). But to try a take off at anything below normal speeds is surely inviting disaster?

[18-Wheeler]

V1 is based on the full (or planned) length of the runway. If some twit taxies out in front of you, then that figure is not worth anything.
If you can't stop in time then it may well be worth getting the plane into the air at a speed at which it will physically fly. It'd be better to do that than to run into another plane when one or both have a lot of fuel on board.
That's why they pay us to make decisions like that.
I know what the plane can really do, so I am better equipped to make the decision whether to try to stop or try to go, rather than make a seat-of-the-pants one based on sheer guesswork.

[john_tullamarine]

Given the sort of height to be cleared, I would put my money on stopping performance EVERY time in a crossing situation detected prior to V1 - the risk outcomes warrant avoiding a highspeed impact at all costs ...... there was a celebrated almost disaster at Sydney years ago ... as I recall a domestic 727 was faced with this sort of situation when an international DC8 (?) took a wrong turn and crossed the active in front of the accelerating 727.

Post accident analysis indicated that stopping would have been a doddle. In any event the crew, faced with a situation for which they had no knowledge or training, took a punt and went for the continued takeoff ... the result was that the tail of the 8 ripped the belly out of the 727. The 727 crew then did an excellent job of recovering the situation.

They were, of course, crucified at the enquiry and in subsequent legal proceedings .....

[mutt]

You either have a V1 or you don't. Not exactly, there are a range of V1's, most operations are conducted at a Balanced V1 for the sake of convenience. There is also a Minimum V1 where you can have an engine failure and still reach V2 and a Maximum V1 where you can still stop on the available runway!

Mutt.

[PAXboy]

carl josef
"Sorry, maybe I should have asked this question in the Flight Testing forum.
Is there any objection to put it there too?"

Yes!!
The moderators and Chief Pilot of PPRuNe, do not like the same subject being debated in two threads at the same time. This makes more work for the server and slows performance. Which means that it takes Danny longer to get airborne but I don't know by exactly how many metres. :p

[SASless]

It must get awfully boring on layovers.....!

[Silver Shadow]

The de-rated heavy weight average time from TOGA to liftoff is just over 50 seconds. Considering liftoff speed at heavy weights is about 175 knots, then that's a distance of about 2500 metres give or take.

It sounds like you want to know the minimum unstick speed carl. In testing they whack an almightly piece of wood on the tail and drag it along the runway until the thing lifts off. It's the minimum fly speed, and you really don't want to see it. At a rough guess it's about 140-50 knots at heavy weights.

There have been a number of incidents where some twit (as you put it 18 wheeler!), has taxied in front of an aircraft taking off. One particular case I have heard about was after V1 but before VR. The aircraft was snatched, scraping both the tail, and engine #1. Both aircraft involved were 747s.

There was an incident at sydney were a 747 was towed across the runway in front of another 747 taking off. The aircraft was able to rotate normally and managed to clear the taxiing plane. Had it been a heavier wieght though!

I guess you could go for the parallel taxiway...

SS