More Finnair woes
Join Date: Aug 2005
Location: ME
Posts: 250
Likes: 0
Received 0 Likes
on
0 Posts
V1 phenomenon
Ok, it's time to ask a question, related to the conversation.
Let's look at a V-Speed Table of my B747-300. For example, for the weight of 250t in one of the temperature columns V1 is 124kts. Moving up in the same column we see V1 = 160kts with TOW = 360t.
RW is long, elevation is low, so we can takeoff with TOW = 360t and performance calculations guarantee that should we abort at V1 we will safely stop withing the RW limits.
Then, company changed plans, deplaned passengers, offloaded cargo and even defueled the aircraft. We are 250t now. The same day, same runway. V1 is 124kts.
The question: Why the hell it's safe to abort at 160kts in the end of the RW and NOT safe to abort at 125kts in the middle:
Let's look at a V-Speed Table of my B747-300. For example, for the weight of 250t in one of the temperature columns V1 is 124kts. Moving up in the same column we see V1 = 160kts with TOW = 360t.
RW is long, elevation is low, so we can takeoff with TOW = 360t and performance calculations guarantee that should we abort at V1 we will safely stop withing the RW limits.
Then, company changed plans, deplaned passengers, offloaded cargo and even defueled the aircraft. We are 250t now. The same day, same runway. V1 is 124kts.
The question: Why the hell it's safe to abort at 160kts in the end of the RW and NOT safe to abort at 125kts in the middle:
Last edited by Romasik; 16th Dec 2010 at 09:37.
Join Date: May 2008
Location: Hang on, let me check the FMS...
Posts: 195
Likes: 0
Received 0 Likes
on
0 Posts
At the lighter weight, are you not now restricted by VR? So your V1=VR as VR cannot be greater than V1
My two cents: Above V1 you go. Simples.
You can type all these extreme scenarios on your keyboard, but most of them will be so abnormal that your 'decision' to stop above V1 on the day would be more of a guess as you would not have the time to correctly diagnose the situation.
The difference between great airmanship decisions and great stupidity is often just luck.
My two cents: Above V1 you go. Simples.
You can type all these extreme scenarios on your keyboard, but most of them will be so abnormal that your 'decision' to stop above V1 on the day would be more of a guess as you would not have the time to correctly diagnose the situation.
The difference between great airmanship decisions and great stupidity is often just luck.
Thread Starter
I really wonder how this discussion on aborting above V1 can come up every now and then on this "P" forum.
The numbers speak fo themselves - how many overrun accidents and incidents due to some crew deciding they know better ? And how many 'heroic saves' achieved through 'superior airmanship' in one of those 0.00000x likelihood scenarios?
Btw a double engine flameout (assumed on a twin) after V1 does not apply as an example. That is a catastrophic failure that will inevitably lead to an accident, there is no choice to abort or not. Only the seriousness will depend on the remaining runway length and the terrain beyond.
The numbers speak fo themselves - how many overrun accidents and incidents due to some crew deciding they know better ? And how many 'heroic saves' achieved through 'superior airmanship' in one of those 0.00000x likelihood scenarios?
Btw a double engine flameout (assumed on a twin) after V1 does not apply as an example. That is a catastrophic failure that will inevitably lead to an accident, there is no choice to abort or not. Only the seriousness will depend on the remaining runway length and the terrain beyond.
Join Date: Jan 2003
Location: Manchester
Age: 45
Posts: 615
Likes: 0
Received 0 Likes
on
0 Posts
There appears to be some serious thread drift here.
From what I have read it seems as if the runway lighting was hit way below V1, so the quetion is why did they continue their T/O roll and not stop below V1.
From what I have read it seems as if the runway lighting was hit way below V1, so the quetion is why did they continue their T/O roll and not stop below V1.
Ladies and gentlemen, if I may remind you that discussion about abort above V1 on PPRuNe have so far always ended in producing so low wheat to chaff ratio that JT had no option but to lock the offending threads. Please, let's not walk the path to the thread graveyard once again, especially as we have no reliable info on the speed at the time of the occurrence.
Let's wait for Statens Havarikommisjon for Transport and/or Onnettomuustutkintakeskus to supply us with some factual information before letting our imagination run wild, please.
Let's wait for Statens Havarikommisjon for Transport and/or Onnettomuustutkintakeskus to supply us with some factual information before letting our imagination run wild, please.
