View Full Version : Which rwy has higher MTOW
grind king
28th Dec 2004, 01:23
Which runway has a higher MTOW as "limited by second segment climb"? Why?
A. 12000ft
B. 6000 ft
C. Both the same
Intruder
28th Dec 2004, 02:53
"limited by second segment climb"
C.
How much climbing do you do on the runway?
The assumption is that you are at least at 35' at the end of the runway when the subsequent climb segments are calculated.
Answer A, the additional runway length will permit you to use improved climb/overspeed/optimized V-speeds to achieve a higher speed on the ground, therefore increasing your second segment climb ability and weight.
Mutt.
john_tullamarine
28th Dec 2004, 05:56
... subject to the
(a) particular aircraft's AFM including scheduled V2 overspeed data ... some do ... some don't.
(b) same Hp, OAT.
enicalyth
28th Dec 2004, 07:34
Well in the spirit it is being asked, like a pilot's pub quiz, since no aircraft is quoted I'd go along with Mutt or else the quiz is a fix in which case I want my dollar back! Didja hear no jets landed at YSSY yestiddy? Naw! Yup, only turbofans and turboprops!
Depends on aircraft type, could exceed the tyre speed on a 6000 ft strip or 12000ft strip if using the the additional runway length for improved climb/overspeed/optimized V-speeds.
Only three factors really effect takeoff aircraft/engine performance...aircraft weight, density altitude, and temperature.
:ok:
I think that we would all agree that its an incomplete question with various correct answers..... therefore it has to be a JAA exam question. :):)
Mutt.
Old Smokey
28th Dec 2004, 22:06
Yes mutt, it's an incomplete question, but yours is the best response so far.
From another perspective, even if not Field Limited on the 6000 ft runway with the "Increased" Takeoff speeds available (Which I assume to be the case as the original poster refers to Obstacle Limit Only), the 12000 ft runway still wins from the obstacle perspective.
Even if the aircraft was capable of the Structural Limit as the maximum field limit (even at the increased speeds) on the 6000 ft runway, then, at the same weight on the 12000 ft runway, the obstacles are a further 6000 ft distant, thus requiring lesser obstacle clearance gradient for their clearance. The only exception to this is a very UP sloping runway where the 1st segment obstacle may be the runway itself, with essentially level ground beyond and close-in (This happens on a few very long UP sloping runways that we use (Melbourne RWY 34 for example at +0.9% where the aircraft 'basic' 1st segment gradient might only be of the order of +0.5%, and weight must be reduced to achieve satisfactory 1st segment clearance)).
Too many variables, here's one more of them.
Happy New Year to all,
Old Smokey
Intruder
29th Dec 2004, 04:08
From another perspective, even if not Field Limited on the 6000 ft runway with the "Increased" Takeoff speeds available (Which I assume to be the case as the original poster refers to Obstacle Limit Only), the 12000 ft runway still wins from the obstacle perspective.
Except that when you look in the RPM, the Climb limit on MTOW is independent of runway -- it's a separate column altogether! Therefore, if the controlling factor is second-segment climb, and NOT the runway, then runway length is irrelevant! :8
Old Smokey
30th Dec 2004, 04:00
Intruder,
I was referring to the case where you "get off" in 6000 feet, and then have a further 6000 feet of runway beneath you in the 1st/2nd segment climb. If sufficiently Up sloping, this remaining runway then becomes an obstacle to be considered in 1st/2nd segment climbs. It is VERY VERY relevant, and, as stated IS the limiting obstacle for several runways that we operate from. If sufficiently UP sloping, the aircraft would crash back into the runway obstacle during the 1st segment climb. Melbourne Australia RWY 34 is a prime example.
Regards,
Old Smokey
CJ Driver
30th Dec 2004, 16:35
the aircraft would crash back into the runway obstacle
I've been looking for a new explanation for some of my firmer landings, and now I think I've found it. We didn't land - we crashed into the runway obstacle!
On a slightly more serious note - presumably if airborne in the first 6000 feet, followed by loss of an engine, followed by actually settling back onto the (uphill) second 6000 feet, would one have the presence of mind to choose whether to stop or keep going?
maxalt
1st Jan 2005, 04:05
If this was purely a multiple choice question I'd choose 'C' as the 'most correct' option.
If it was an interview question I'd consider it an opportunity to display my amazing grasp of a/c performance by describing all the alternatives here listed by my learned colleagues!