Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

Runway behind you.

Tech Log The very best in practical technical discussion on the web

Runway behind you.

Old 16th Jul 2009, 11:03
  #1 (permalink)  
Thread Starter
 
Join Date: Jul 2008
Location: france
Posts: 6
Runway behind you.

I'm a PPL and have often been told that there's nothing more useless than runway behind you before takeoff. I use Marseille LFML, a lot and have noticed a particular airline habitually opting for less than the full TODA, while everyone seems to taxi out to the threshold. Is this for punctuality reasons or am I missing something ?
michaelporteous is offline  
Old 16th Jul 2009, 11:17
  #2 (permalink)  
 
Join Date: Oct 2000
Location: Berkshire, UK
Age: 75
Posts: 8,276
This subject has been done to death on another thread on PPRuNe. Fact is that intersection take-offs are perfectly safe and are employed thousands of time daily at airports all over the world.
HEATHROW DIRECTOR is offline  
Old 16th Jul 2009, 11:58
  #3 (permalink)  
 
Join Date: Jul 2008
Location: Gone to my "Happy Place".
Posts: 157
In a single engine aircraft - which with a PPL I assume is the case - what you've said is true. Runway behind you is worthless...

In two, three and four engine aircraft it's a different story, particularly if that aircraft is certified under FAR / JAR 25.

Intersection departures are perfectly safe - and many times quite cost effective - provided that you have calculated the take-off and climb performance and are able to meet any limitations, etc.

Before I get beat to death about this explanation by the masses, the above is a very simple and brief explanation directed at a PPL who is not attempting to operate a transport category aircraft. There is, in fact, a lot more that goes into it.
Jimmy Do Little is offline  
Old 16th Jul 2009, 12:02
  #4 (permalink)  
Gender Faculty Specialist
 
Join Date: Mar 2002
Location: Stop being so stupid, it's my turn
Posts: 1,709
Safety, performance calculations, expeditious departures and other limitations aside, runway behind you is still useless.
Chesty Morgan is offline  
Old 16th Jul 2009, 12:50
  #5 (permalink)  
 
Join Date: Mar 2006
Location: Choroni, sometimes
Posts: 1,975
Safety, performance calculations, expeditious departures and other limitations aside, runway behind you is still useless.
Yes, useless like altitude above.

So let's stay on the ground.
hetfield is offline  
Old 16th Jul 2009, 12:56
  #6 (permalink)  
 
Join Date: Nov 1999
Location: East side of OZ
Posts: 616
Now if you took off from a conveyor belt there need never be any runway behind you!
Bullethead is offline  
Old 16th Jul 2009, 12:58
  #7 (permalink)  
Thread Starter
 
Join Date: Jul 2008
Location: france
Posts: 6
runway behind you

If I'd been on Emirates A345 tailstrike I would be very glad to have used the whole runway. Why throw away an extra safety margin ?
michaelporteous is offline  
Old 16th Jul 2009, 13:21
  #8 (permalink)  
 
Join Date: Jun 1999
Location: global
Posts: 62
Why fly anything with less than 4 engines then? Or take off when it's raining?
Charlie Pop is offline  
Old 16th Jul 2009, 13:25
  #9 (permalink)  
 
Join Date: Mar 2008
Location: Malvern, UK
Posts: 400
The thing with these wise philosophies of caution, of which "runway behind" is one of many, is that you have to spot when they become ludicrous.

In my early PPL days our school was at Manchester and we shared the runway with the big boys. The earliest intersection from the south side to 24 (only the one runway in those days) was some 500 metres from the threshold. This left my Piper Tomahawk with a mere 2500 metres to get airborne.

I dread to think how a "Request backtrack" would have been received by ATC.
Dont Hang Up is offline  
Old 16th Jul 2009, 13:41
  #10 (permalink)  
 
Join Date: Jun 2009
Location: england
Posts: 47
michaelporteous,
As Jimmy do Little has already said - there is much more to it than meets the eye. If you obsess over every little detail - why cant we do this, why dont we do that - we would never leave our homes, let alone go flying.
The simple answer for intersection take offs are that;
It saves time, fuel aka Money.
Can help ATC when they're busy - more movements.
Performance calculated to ensure that at V1 (just prior!) you can reject and stop. Or continue and reach the minimum screen height.
There are many other performance based issues here too.
These procedures are being used world-wide everyday and are tried and tested otherwise we wouldnt be doing them.
CommandB is offline  
Old 16th Jul 2009, 14:01
  #11 (permalink)  
Gender Faculty Specialist
 
Join Date: Mar 2002
Location: Stop being so stupid, it's my turn
Posts: 1,709
Yes, useless like altitude above.

So let's stay on the ground.
Or fly as high as possible. Like using as much runway as possible.

Runway behind you IS useless because you can't use it. Simple as that.
Chesty Morgan is offline  
Old 16th Jul 2009, 14:16
  #12 (permalink)  
 
Join Date: Jun 1999
Location: global
Posts: 62
You don't get any points for stating the obvious, especially when it's been pointed out ad nauseum why runway behind you is not a problem.
Charlie Pop is offline  
Old 16th Jul 2009, 14:20
  #13 (permalink)  
Gender Faculty Specialist
 
Join Date: Mar 2002
Location: Stop being so stupid, it's my turn
Posts: 1,709
Charlie Pop, I didn't say it was a problem did I?
Chesty Morgan is offline  
Old 16th Jul 2009, 14:42
  #14 (permalink)  
Warning Toxic!
Disgusted of Tunbridge
 
Join Date: Jan 2005
Location: Hampshire, UK
Posts: 4,011
I never take off full length when an intersection take-off is perfectly acceptable- I've got a schedule to keep, so runway behind me is completely useless- I don't want it anyway, thankyou. When I fly, altitude above me is useless- totally useless unless I only want it because some other mother is blocking me from climbing. Other than that, you can keep it, ta v much. Fuel still in the bowser is useless- because I've always had enough. Ain't never come near running out yet- my job is to make sure that doesn't happen.

All in all, yet another trite (alleged) saying passed from mouth to mouth by simpletons that means absolutely nothing, and is destined to waste our time ad infinitum. Is there any way we can put a stop to people spreading this daftness? Like exterminate the culprit everytime? It would die out in a generation.
Rainboe is offline  
Old 16th Jul 2009, 14:59
  #15 (permalink)  
 
Join Date: Dec 2003
Location: Tring, UK
Posts: 1,414
I'd have to agree with Rainboe... It's just another old saying. After all, in a perf. 'A' aircraft, what are you going to use the extra runway for? Stopping after V1 or Vr? We had a graphic demo. recently of how inadvisable that is...

Best bit is that if you are using assumed temperature data (most airlines do) on an average length runway, you'll have pretty much the same margins over the hedge using an intersection as if you'd gone for full length.
FullWings is offline  
Old 16th Jul 2009, 15:02
  #16 (permalink)  
 
Join Date: Jul 2001
Location: Gold Coast
Age: 54
Posts: 1,611
Well that A340 at Melbourne a few months back was very sure that they were going to make it off on the runway available safely, but simply didn't.
It was a rare mistake, that's for sure, but if there's no time pressure I can't see why you wouldn't use that bit of extra runway.
That being said, if all the calcuations are right it's a perfectly acceptable option to use less than the full length.
18-Wheeler is offline  
Old 16th Jul 2009, 16:54
  #17 (permalink)  
 
Join Date: Apr 2009
Location: Petaluma
Posts: 330
So now let's move on to fuel unused at TO. (Flex). It's only unsafe when it is. As Emirates demonstrates, both int. TO and flex demand no bonehead mistakes.

There will always be bonehead mistakes. Against that certainty, eliminating a fix for Mr. Bonehead's play, is worth how much? Someone must know.

Will

Last edited by Will Fraser; 16th Jul 2009 at 17:39.
Will Fraser is offline  
Old 16th Jul 2009, 17:26
  #18 (permalink)  
C-N
 
Join Date: Apr 2007
Location: Tower
Posts: 80
LFML RWY is NOT intersecting, both are in parallel with each other. I'm almost 15years in aviation with nearly 06 years of flying and haven't had heard this quote "RWY behind you".
C-N is offline  
Old 16th Jul 2009, 17:31
  #19 (permalink)  
 
Join Date: Aug 2001
Location: A few miles from the airport
Posts: 219
Do you want to die young *****? I want full lenght.
POL.777 is offline  
Old 16th Jul 2009, 17:53
  #20 (permalink)  
kijangnim
Guest
 
Posts: n/a
Greetings,

In the A340 Australia incident, takeoff weight error, the runway lenght would not have solved the issue, low speed is low speed even if the runway was 10 nm long.
So talking about it doesnot prove that the runway left behind...
 

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.