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OverRun
9th Jul 2002, 10:41
737 takeoff roll and climb gradient - AEO ops normal

What is a typical takeoff ground roll length for a 737? I've got two cases in mind where the full performance engineering has been done to the various FAR 25 and Australian CAO 20.7.1B operating rules:

737-400 at a takeoff weight of about 58 tonnes which needs 1900m TORA (assuming 10 kts headwind, design air temperature, no obstacles, flat and dry runway, etc). This TOW was set for full pax, no freight, 2 hours flight.

737-800 at a takeoff weight of about 77 tonnes which needs 2500m TORA (assuming 10 kts headwind, design air temperature, no obstacles, flat and dry runway, etc). This TOW was set for full pax, no freight, 4 hours flight.

Now I've got the data for the engine-out and minimum climb gradient rules. My question is - ignoring all TORA, TODA, ASDA and climb gradient limitations - what is the typical takeoff ground roll for ops normal?

I dimly remember a rule-of-thumb that it is about two-thirds of the required TORA. For the required TORA of 2000m, the take-off roll might average something like 1333m. For the required TORA of 2500m, the take-off roll might average something like 1667m. Of course it will vary on every takeoff with technique, wind changes, noise, reduced thrust, performance degradation and all the other factors. But still - does anyone have a feel for a typical takeoff ground roll for a 737?

And since we're looking at what happens in an ops normal takeoff (as opposed to the minimum case), what would be a typical climb gradient to 500 or 1000 feet altitude. We've had discussion in this forum last year on "Engine Out Climb Performance". 4dogs wrote that "Most aircraft have to meet a minimum performance requirement of 6% AEO (all engines operating) (see CAO 20.7.4, FAR/JAR 23 and equivalent certification rules).

Now I know we're getting deep into the 'how long is a piece of string' analogy - and everything will vary with flap setting, noise abatement, weight, use of reduced thrust or not, temperature and wind, etc. But for a typical case, no noise abatement, no reduced thrust, reasonable temperatures, 10 kts headwind, the sort of weights I've got above, a bit of realistic airframe and engine degradation, etc - what is the sort of climb gradient that might occur up to 500-1000 feet altitude. I've got a rule-of-thumb from a deal that Front**r Airlines had with an airport in Amer**a, and had they agreed to perform to at least 8.6% whatever reduced thrust they set. Does that mean that 8½ percent is a typical gradient for ops normal?

Appreciate any thoughts
OverRun

mutt
9th Jul 2002, 12:48
For the second part of your question…….

These are taken from the community noise document. Based on ISA, All Engines and max structural takeoff weight the following climb gradients should be available at 1000 feet.

B747-400, 10% climb gradient at takeoff power, reducing to 6.5% at climb power.
B777-200, 13.8% climb gradient at takeoff power, reducing to 8.5% at climb power
B757-200, 14.5% climb gradient at takeoff power, reducing to 10% at climb power

The newer B737 aircraft should have similar gradients to the 757/777.

Mutt..

john_tullamarine
9th Jul 2002, 13:31
Overrun,

From your post I presume that you have access to the AFM and Boeing Crew Manuals relevant to your particular aircraft/engine cocktails ... as you are presumably either DJ or QF, that probably indicates that you are in management or closely aligned .. ? .. as I presume both carriers use the CAR exemption permitting the non-carriage of AFMs.

The crew manuals may give some gross performance data from which you can obtain an approximate or specific ground roll.

Alternatively, if the particular AFM has data for TOR2 and TOD2, then you can get a reasonable idea by comparing two data points for the same configuration, conditions, weight, etc., by the following means

(a) figure the AFM TOR2 and TOD2 values for the case in question. If you want to figure in a non-zero wind, you will need to adjust the way you use the AFM wind carpet either by entering at twice the headwind, or two-thirds the tailwind to account for the normal 50/150% wind fudge factor.

(b) reduce each value in (a) by the 15% AEO factor

(c) calculate the resulting difference

(d) reduce the "de-factored" TOR2 calculated in (b) by the difference calculated in (c)

... should be within a reasonable bull's roar of the answer you seek ....

... alternatively, I could be persuaded to do the sums for you for a small consideration of a beer or two (GST ignored) ... are you likely to be crewing the DJ flight I am paxing on tomorrow ? ... give me something to do in cruise ....

Looking at your concerns with bugsmasher climb performance, the current FAR23 requirements are along the lines of

4% (bigger piston and turbine) for gear down T/O configuration at SL
8.3% (smaller piston) for gear up T/O configuration at SL

The 6.0% ANO 101.22 (the local additional requirements implementation of FAR 23) was an Oz requirement to fit in with airfield standards. I just can't remember what the CAR/FAR requirements were back then in the absence of an archive search. I am pretty certain this isn't relevant to .. and never applied for heavies ....

(modified to keep Mutt happy ....)

OverRun
10th Jul 2002, 04:07
Mutt,

Thanks for those gradients - exactly what I was looking for.

Makes me wonder how well we manage community relationships. Historically, when aircraft performance is discussed with town planners and local councils, the only response we can give is about engine-out performance and obstacle clearance gradients. This conjures up images in the lay mind of aircraft screaming above the treetops on one engine, with flames pouring out of the other. The reality as we know is quite different - in normal operations, aircraft climb out smartly and are soon well above the obstacles.

For what it's worth, I've started handling such discussions by using the concept that there is a "buffer zone". Something like this: the obstacle clearance gradients are there to establish a buffer zone between the aircraft and any obstacles. In normal operations, the aircraft flies well above this but the buffer zone provides the necessary margin of safety for all conditions. It takes the emotion out, and makes for a more productive discussion [too late for Sydney Airport though :D ].


john-tullamarine

Thanks for the suggested method of calculation. I haven't got the AFM or crew manuals (being neither management nor closely aligned), and TOR2 and TOD2 have got me a bit stumped :confused: - are these TORA and TODA or something more refined? I got my data from the full performance calculations by the Eagle, Takeoff Weight and other QF and AN Ops programmes.

If you have the chance to while away some time in DJ cruise (as an alternative to the face painting) and look at the two cases, I'd appreciate it and would indeed owe you a frosty or two. Zero wind and assuming all other factors neutral is fine.

OverRun

john_tullamarine
10th Jul 2002, 10:29
Guess that I can't guess it right more than some of the time ....

TOR2/TOD2 = takeoff run/takeoff distance with both motors working

Not able to do the sums without a flight manual ... I have some 400 data in the files but no 800 .. but won't be back in the office for a while ... I presume you are in Sydney ... if so we could always have the beer in advance ...

Mutt may have the data to hand ... see what he comes up with ...



Just realised that I have no idea to what the "face painting" reference is ? perhaps you can enlighten me

... my first trip on DJ and on a -700 ... OK except the seats are too narrow for my modest bulk ... but a mark of 110 percent for the touchdown in quite gusty conditions .... and the two girls in the front of the cabin did a more than acceptably professional job as far as I could see ....

mutt
10th Jul 2002, 11:52
Thanks for clearing that up JT, (next message)



http://www.stopstart.fsnet.co.uk/smilie/guin.gif.

Mutt.

john_tullamarine
10th Jul 2002, 22:17
I suspect distance to VLOF ..

OverRun
11th Jul 2002, 01:11
Face-painting? in-between selling peanuts and Richard's autobiography, the DJ girls can often be found right down the back of the cabin, facepainting the kids. It's just not like the old days . . . . :)

Good graphics link Mutt - this vB code just slays me - http://www.stopstart.fsnet.co.uk/

http://www.stopstart.fsnet.co.uk/aircraft/Runway.gif