View Full Version : TODR/TORA/TORR/ASDR Definitions without any ambiguity please !!!

31st Mar 2003, 19:28
Hi there eveyone , need a lile help with regards to the definitions of the following ...one prerequisite is that none of the definitions should have any ambiguity in any sense .

1.TODA - Take off distance avaiable

2.TODR - T/O dist required

3.TORR - T/O Run Reqd

4.Landing Dist Reqd



7.ASDR - Accelerate Stop distance required

8.ASDA -- Accelerate stop distance avaiable

9.Balanced Field Length

10.Climb Gradient and its effects on performance .

11.What limits your the amount of fuel u can carry other than Passengers and cargo & MLW & Field length ? Would it be right to assume that Wing root strength would limit your MZFW ?

Thanks in advance . All are welcome to post .

31st Mar 2003, 22:27

I have rearrange your Qs to improve the flow.

6. STOPWAY An area beyond the takeoff runway no less wide than the runway and centered upon the extended centerline of the runway, able to support the airplane during an aborted takeoff, without causing structural damage to the airplane, and designated by the airport authorities for use in decelerating the airplane during an aborted takeoff. It is NOT inclucded in TORA.

5. CLEARWAY - A defined rectangular area on the ground or water, at the departure end of the runway selected or prepared as a suitable area over which an aeroplane may make a portion of its initial climb to a specified height. This WILL include the Stopway if there is one.


2. TODR - Depending on the ambient conditions and your weight, your TODR must be < TODA to takeoff successfully.

3. TORR - Depending on the ambient conditions and your weight, your TORR must be < TORA to takeoff successfully.


7. ASDR - Depending on the ambient conditions and your weight, your ASDR must be < ASDA to remain on the confines on the runway during an abort.

9. Balanced Field Length - TORA = TODA ie. no CLEARWAY

4.. LDA (Landing Distance Available) - RUNWAY minus Displaced Threshold (if any)
LDR - needs to be < LDA to remain on runway during a landing.

10. This Q will require a much longer posting to cover. Basically, for your TOW, you must be:
a) able to get airborne by the end on your TORA.
b) reach a screen height of 35' by the end of your TODA
(all these assuming you suffered an engine failure) and;
c) stop at the end of the STOPWAY if ypu elect to abort prior to V1.
That's what performance is all about.

11. For each takeoff, your TOW is usually limited by either of:
a) Performance Limited (usually Field Length, Climb or Obstacle)
b) Structural Limit
c) Landing Weight Limited
d) Zero Fuel Limited

Hope this helps...


1st Apr 2003, 00:25
Hi there Super , that was very kind of u to respond , it does make things clearer for me. But I still have this question of whether or not wing root strength limits the ZFW ? We had this appear in a JET AIRWAYS EXAM and the correct answer apparently was that it does. Can anyone shed some light on this topic ? Thanks once again.


PS Does anyone have a JPG image or file depicting the distances diagramatically ???

1st Apr 2003, 01:59
The short answer:

ZFW is published by the manufacturer. It's one of many structural limits, in this case due to the wing root strength.

Imagine an a/c in flight being supported by the wings (ie two sets of forces acting upwards). A majority - but not all - of its weight is in the fuselage (ie a force acting downwards).

There will be a large amount of structural load on the wing roots as the wings & the fuselage try to move in opposite directions.

The more weight in the fuselage the greater the load. Eventually something will break. Weight in the wings eg fuel, does not contribute to this strong bending force hence once the the MZF is reached any extra weight must consist of fuel.

The presumption is that fuel only goes into the wings. Of course fuselage & empenage tanks are quite common and are considered when MZF is set by the manufacturer.

For the long answer see the other thread about ZFW that's running.

1st Apr 2003, 11:09
11. For each takeoff, your TOW is usually limited by either of:

e: Pavement strength.


1st Apr 2003, 15:33
Hi tin and mutt , thanks a bunch for the replies . Your explanation about the topic tinstaafl was really useful in helping me understand the problem and they way we work around it.


7th Apr 2003, 21:52
err SuperRanger,

about No 9 "Balanced Field Length" - TORA is misleading, as is the 'no clearway' statement.

Balanced Field length is when ASDR = TODR and that portion of clearway that overlies stopway can be considered. In short, when you get to V1, the distance required to go is the same as the distance required to stop.

It is an often debated topic easily unearthed with the Search function.

9th Apr 2003, 18:58

you're absolutely right... ASDR=TODR is a much better definition. just that TORA=TODA seem to have edge itself onto my brain... :)