Toda

[Groundgripper]

A quick question to which I should know the answer, but it's been many years since I last did any civil aircraft performance calcs - what does TODA stand for in relation to runway length?

Come to that, does anyone know of a website which covers aviation abbreviations? Could save a lot of embarrassment on my behalf!

[Findo]

When I left the airports some years ago it was Take Off Distance Available = the Take Off Run Available (the tarmac bit) plus any cleared or graded area beyond that (over which you can fly coz you really should have all your wheels off the ground by then !! )

[FlapsOne]

I beg to differ.

TODA = Take Off DISTANCE Available.

The length of the take-off run available plus the length of the clearway or stopway.

TORA = Take-off RUN available (TORA).

The length of runway which is declared available and suitable for the ground run of an aeroplane taking off.

[682ft AMSL]

I thought Findo's definition was correct - as evidenced by the published figures for the 2250m RWY14 at Leeds.

TORA - 2113m
TODA - 3169m

Basically, get your wheels off the ground before the tarmac runs out and the next obstacle you come across is the best part of another 1000m along.

What that obstacle is, I've no idea. Local talk has always been that if you depart from 14 at Leeds, put the wheels up, climb no further and maintain runway heading, the first obstacle you hit is the Alps!!

682

[Groundgripper]

Ah, yes, it's all slowly coming back now. Info was requested by daughter in law who is going for an interview tomorrow morning.

I seem to remember that TORA includes an allowance for the aircraft to climb to a height of 35 or 50 feet to clear obstacles at the end of the runway, so is significantly less that the physical length of tarmac available (TODA).

Many thanks to all.

Regards

GG

[Findo]

Flaps one - we have said the same thing.

TORA - you are on tarmac

TODA - you have used all the tarmac and you are over a bit of ground where there are no trees or hills but get your ass higher in the air before you meet something.

[TheFox]

IIRC a TODA can be no bigger than 1.5 x TORA

[Helen49]

TODA = TORA + Clearway
Stopway is irrelevant with regard to TODA except that it may be part of the area designated as clearway.
ASDA (ED) = TORA + Stopwa

[FlapsOne]

Findo

I re-read your post and do agree they are, more or less, the same thing - apologies!

[bookworm]

So here's a trivia question for you:

When does EDA exceed TODA? Or put another way, when is a stopway not a clearway?

[Tinstaafl]

A clearway doesn't have to be suitable for an aircraft to roll along it. It could have ditches, soft ground, lakes etc.

A stopway has to meet some sort of criteria for allowing the a/c to roll along while coming to rest. It may be constructed to collapse in a manner that aids bringing the a/c to a stop.

[john_tullamarine]

One consideration -

TORA includes ALL the runway bit but doesn't infer that you will be dragging the bird off the ground as you go into the grass ... TORR requires either 33% or 50% (depending on the rules) of the airborne distance to screen to be above TORA... the rest of the flare distance to screen may then be over the clearway, if such is declared for the runway ....

..... to make sure that you are likely to get off the ground without kicking up a cloud of dust ...

[m&v]

682........As a visiting(summer season)320 crew dept off 32 was 'limited' to the eng/out climb gradient and obstacles(royalty pub)as one turned to aheading of 020..Off 14 the next obstacle was the Alps,so one occasionally took off with a 10k tailwind,increase flap,to move the load.
As JT says regs require that half the distance from VR to the 'screen' height must be over runway-which makes one wonder how high one actually is,over the end of the runway, to meet the 15'screen'at the end of the 'clearway'??

[john_tullamarine]

.. ah ... how high you are depends on a bunch of variables and just which limit is the limiting case for the particular takeoff.

(a) ASDR - hopefully no height at all
(b) TOD1 - probably a bit above 35/15 ft
(c) TOD2 - moderately above 35/15 ft
(d) TOR1/2 - depends on the C/W declared and the aircraft

and so forth ...

The actual height at the end of TORA will vary a bit and, unless you have some flight test data, you can only make educated estimates .. as a first approximation, half the screen for the 1:1 rules.

[bookworm]

When does EDA exceed TODA? Or put another way, when is a stopway not a clearway?

A clearway doesn't have to be suitable for an aircraft to roll along it. It could have ditches, soft ground, lakes etc.

A stopway has to meet some sort of criteria for allowing the a/c to roll along while coming to rest. It may be constructed to collapse in a manner that aids bringing the a/c to a stop.

Ah but you've just told me when a clearway might not be a stopway. The riddle of the day is about when a stopway is not a clearway.

No takers?...

[Tinstaafl]

When it has arresting gear/crash barriers that are too high to meet clearway criteria?

Or when the stopway is long enough to exceed the clearway's max. length limit?

[Keith.Williams.]

Another possibility is that there is an obstacle off-set to one side of the stopway. The minimum stopway width is the same as the runway it serves. But the clearway must be somewhat wider (the actual figures depend on who's regulations you are using). So an obstacle that is not on the stopway, but is close to one of its sides, will limit the length of the clearway, but allow the stopway to continue.

[bookworm]

Another possibility is that there is an obstacle off-set to one side of the stopway.

That was exactly the case I was thinking of Keith. You get the virtual champagne -- cheers...

I believe that's what limits e.g. Heathrow's 23 to a TODA of just 1243 m while it has an ASDA of 1962 m.

[OverRun]

Intriguing discussion. Bookworm's question has got the grey matter thinking and Keith earned his virtual champagne.

The following simple ICAO picture shows a few examples for future reference for interviews:

[bookworm]

FWIW, I became aware of the issue only after reading a Eurocontrol document (on ARINC <-> AIXM mapping) that appeared to claim that TODA was TORA + stopway + (extra) clearway. That one-dimensional picture is not quite sufficient. OverRun's case E is a bit more explicit, in that it at least hints that CWY coould be shorter than SWY.

(For the record, I think the Eurocontrol team did an excellent job of AIXM.)