PifPaf
9th Mar 2003, 21:14
Since I left fighters to fly airliners, one question was unsolved for me: why don´t we have two different speeds to decide to reject or continue takeoff?
This issue bothered me much more after Concorde´s accident at Gonesse.
All of you know that we could have different “Vee-ones” for climb and field restrictions. On 2-eng fighters, this two speeds are taken into account. The first one is called “go/no-go” (or decision) speed, while the other is “refusal” speed. If you have an engine failure before “go/no-go”, you must RTO. If you experience the failure after “refusal”, you must proceed. But, if the engine fails between go/no-go and refusal, it´s at pilot´s discretion to reject or continue takeoff. You can either stop on the remaining RWY lenght or check 35ft at the end of the TO distance.
On conventional jets, its easy to understand that we have “slow” V1’s because it must be lower than VR. And what about a high-performance acft like Concorde?
I found out that at Gonesse´s accident, the calculated TO speeds were V1: 150 Kt, VR: 198 Kt, V2: 220 Kt.
We can see that there was a considerable interval between V1 and VR. It´s very easy to conclude that they couldn´t continue before 150 Kt. But what about abort some knots after it?!?
I presume that 150Kt was the minimum airspeed, due to climb restrictions – am I right? If so, and considering that CDG has a very long RWY, I still think that they could have another speed (between 150Kt and 198Kt) until which they could stop the big bird (respecting, of course, field and brakes limits).
Maybe I´m just wondering and Conc arleady has these two V1´s...
I´d appreciate any comments.
Best regards,
PP
(sorry for any offense to Shakespere´s language!):O
This issue bothered me much more after Concorde´s accident at Gonesse.
All of you know that we could have different “Vee-ones” for climb and field restrictions. On 2-eng fighters, this two speeds are taken into account. The first one is called “go/no-go” (or decision) speed, while the other is “refusal” speed. If you have an engine failure before “go/no-go”, you must RTO. If you experience the failure after “refusal”, you must proceed. But, if the engine fails between go/no-go and refusal, it´s at pilot´s discretion to reject or continue takeoff. You can either stop on the remaining RWY lenght or check 35ft at the end of the TO distance.
On conventional jets, its easy to understand that we have “slow” V1’s because it must be lower than VR. And what about a high-performance acft like Concorde?
I found out that at Gonesse´s accident, the calculated TO speeds were V1: 150 Kt, VR: 198 Kt, V2: 220 Kt.
We can see that there was a considerable interval between V1 and VR. It´s very easy to conclude that they couldn´t continue before 150 Kt. But what about abort some knots after it?!?
I presume that 150Kt was the minimum airspeed, due to climb restrictions – am I right? If so, and considering that CDG has a very long RWY, I still think that they could have another speed (between 150Kt and 198Kt) until which they could stop the big bird (respecting, of course, field and brakes limits).
Maybe I´m just wondering and Conc arleady has these two V1´s...
I´d appreciate any comments.
Best regards,
PP
(sorry for any offense to Shakespere´s language!):O