View Full Version : ATPL Performance Question
Taken from an Italian question bank. Could someone explain how you get to this answer? Only one I've found which a few of us can't arrive at happily.
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An airfield has a TORA of 3,000m with the first obstacle (that protrudes above an upward slope of 1.25% from the end of the runway) 6,560ft away. What would the TODA be for an aircraft with 3 turbojet engines?
a) 4500ft
b) 5000ft
c) 14760ft *
d) 16400ft
* Answer is C. How? :)
Spotted the obvious trap of 3000m needing to go to feet but don't know which factor to apply to the distances to arrive at C.
Something similar on Bristol question bank too with no explaination apparantly.
Appreciate the help.
Alex Whittingham
26th Jan 2008, 12:41
The maximum TODA is one and a half times the TORA, 3000 x 1.5 = 4500m, converted into feet to match the answers.
Hmmmm I can't see that in the Oxford book at first glance anywhere you'd expect it. Grr.
Thanks for the help Alex! Fingers crossed it comes up now :)
Keith.Williams.
26th Jan 2008, 14:25
ZYOX
Your Oxford notes probably tell you it in an indirect way.
Such as:
a. The TODA = TORA plus Clearway
b. The maximum allowable clearway = 50% of TORA.
Putting these two together gives you maximum TODA = 1.5 x TORA.
Ah yes. Found it on page 13-3 taken directly from JAR-OPS 1.490
"Take-off Distance required must not exceed the Take-Off Distance available, with a clearway distance not exceeding half of the Take off Run available"
Well deduced Keith, cheers :) Feckin' sneaky one though. They don't elaborate or cover it anywhere else and it's come up a few times in questions. Had it on some ground school notes though, with a side note nicely pointing out that it's 1.25 x TORA (if there's no clearway of course) for Single Engine Pistons.
I'd give anything to be back in the days of only have to remember which was bigger, Vx or Vx >_<
Keith.Williams.
27th Jan 2008, 09:15
I think that you need to take care in reading your notes.
The 1.25 factor is not relevant to the question that you have asked. It does not apply to the TODA, but to the Take-Off Distance or TOD. If there is no stopway and no clearway you multiply the TOD by 1.25 to get the TODR, which must not be greater than the TODA (which with no stopway and no clearway is equal to the TORA).
The TODA is the Take-off Distance Available.
The figure that comes out of the take-off graphs is called the Graphical Distance.
The TOD is the Graphical Distance increased by the surface and condition factors.
When you then increase this by the Regulatoty factor you get the TODR. This must not be greater than the TODA.
The 1.25 regulatory factor (paragraph 2.1.1 (a) in the CAP 698) applies only when their is no Stopway and no Clearway.
If a Stopway or a Clearway exist then you must use the other factors listed in paragraph 2.1.1 (b)
These factors also apply to multi engine aircaft.
Hmmm no I took that figure from a consolidation course where they told us that, or obviously weren't clear enough on what exactly it was.
Time to go over these distances in a little more detail I think...
SYYHerring
27th Jan 2008, 23:35
Read thrice then read again.