TODA and TORR??

[Mr Garrison]

Hi All,

Both take off charts (Cessna and Turbo Lance) for the CPL(A) Operations, Planning and Performance exam specify the Take Off Distance Available (TODA) that the aeroplane needs under certain conditions.

What I find misleading is that the TODA is the TORA plus the clearway (if any).......but what happens if the TORA (Take Off Run Available) is 500M and the TODA is 1000M?? This may satisfy the TODA figure extracted from the charts but what it doesn't tell you is the Take Off Run Required (TORR). In this case we may need a TORR of 700M of runway to accelerate along before we start pulling back on the stick......and for this example there is only 500M so this would surely result in a crash!

How do I assure myself that there is adequate runway available to meet the TODA performance requirement extracted from the graphs? or should I assume that the TODA figures published in these performance graphs do not take into account clearway??


Thanks


Mr G

[avguy1]

If you can't find the TORR you need to use the TORA as your TODA.
Av

If you can't find the TORR you need to use the TORA as your TODA. IE you cannot plan to use the clearway
Av

[Capt Claret]

Mr Garrison

I seem to recall that back in the good ole clearways were a maximum of 60m. However a search for Clearway on the CASA Rules & Regs CD brings up many hits. The quote below from Manual of Standards Part 139-Aerodromes (Chapter6 Physical Characteristics), may give you part of the answer. Please note though,my search is not exhaustive and might not contain all the relevant information!

6.2.31 Location of Clearways
6.2.31.1 A clearway must start at the end of the take-off run available on the runway.
6.2.32 Dimensions of Clearways
6.2.32.1 The length of a clearway must not be more than half the length of the take-off
run available on the runway.

Further CAO 20.7.2, AEROPLANE WEIGHT AND PERFORMANCE
LIMITATIONS — MULTI-ENGINE AEROPLANES NOT ABOVE 5700KG – REGULAR PUBLIC TRANSPORT OPERATIONS, refers to clearway when it defines TODA thus; take-off distance available means the length of take-off run available plus,
where clearway is provided, a maximum of 60 metres of clearway.

Other references in the Manual of Standards Part 139 suggest that TODA is the length of the TORA plus any clearway provided. I cannot find a reference stipulating the maximum amount of clearway for SE ops so would assume the scenario you gave could not happen as the clearway can't be more than 50% of the TORA.

As AVguy has said, if your aircraft charts don't give TORR data, consider TORA as TODA.

[Mr Garrison]

Cheers avguy1 and Capt Claret


:ok:

[john_tullamarine]

TOR calcs are relevant to heavy aircraft - part of the suite of requirements which has to be addressed in determining the RTOW. Generally not of any relevance to light aircraft.

I would be surprised, in the extreme, if you came across any runway short enough to present a problem with other than a nominal RESA clearway... perhaps you can nominate such an example for interest ?

As indicated by others, the aerodrome design Standards place limits on the maximum declared clearway .. in general, because of the additional responsibilities on the aerodrome owner, I wouldn't expect any aerodrome to waste time on clearways (much greater than the normal 60m minimum) unless the runways were intended for heavy aircraft operations ... in which case the lightie pilot probably need not worry too much about the specifics being discussed in this thread.

If you have any concerns then, as suggested by others, use the greater of declared TORA and ASDA in lieu of TODA, while observing any specific requirement such as 20.7.2 .. with the provisio that you would be wise to consider if any allowance might need to be made if part of the runway is seal or the over run area is, say, gravel, and the main runway is seal. General finger in the wind value for air distance to 50ft with a lightie is 150-300m, depending on weight and density height.

However, a very wise question to consider .. most pilots at the newer end of the scale wouldn't be aware of the distinction, I suspect .. do you have an airports or engineering background, perhaps ?

I have sent a note to OverRun (general all round good guy and airports design guru) to see if he might be able to throw some more words into the discussion ....

[OverRun]

Sorry about the delay in getting back. I’m in deepest Africa right now with a steam driven modem. The most pressing aviation problem here is buffalos camping on the runway. They drop lots of bullsh*t (seriously) and it turns out that as it dries, the shrinkage of the droppings or patties of the stuff is greater than the elasticity of the runway bitumen and so it pulls clumps of the runway surface out, and the runway ends up with potholes. Back to civilised issues and TORR . . .

As Avguy1 said above: “If you can't find the TORR you need to use the TORA as your TODA.” That is the safest solution for world operations.

In Australia, there is a firm requirement for a minimum 60m clearway for all runways, meaning that the TODA is at least TORA+60m. It is reasonable to simply add 60m to the TORA and use that as the TODA. Or, as john_tullamarine has said, use the greater of TORA and ASDA (because they both contain the implicit assumption that the ground/runway can support the weight of the aircraft). The TORA, ASDA and TODA distances are published in Australia in the ERSA document.

There is a picture of how the distances fit together at an earlier thread
http://www.pprune.org/forums/showthread.php?s=&threadid=112264&pagenumber=2

Long clearways are not as common these days – the UK seems to be one of the authorities which favour them – one extreme example is RWY14 at Leeds: TORA - 2113m TODA - 3169m.

As far as aircraft below 5,700 kg are concerned, they impart about the same or less load on the surface as the airport maintenance truck does, so if your prop doesn’t strike the ground and there isn't a ditch when you inadvertantly run into the clearway, you can theoretically taxi over the areas where the airport trucks go.

[Mr Garrison]

Perfect!

Thanks for that Overun

;)