10 ms·

My understanding is as follows: If you're on the runway then once you go past V1 during take-off you have no option but to get airborne regardless of what else

by pja 13y ago

My understanding is as follows: If you're on the runway then once you go past V1 during take-off you have no option but to get airborne regardless of what else is happening: there isn't enough runway left to stop the aircraft with the brakes + reverse thrust. (You calculate V1 for every take-off) The pilots he was training were coming from an aircraft with a V1 around 80 knots fully laden. V1 for a 737-400 is around 120 knots so if he triggers an aft cargo door warning at 100 knots then the pilots should abort the takeoff. He was doing this deliberately to emphasise to the trainees this particular difference between their old aircraft and the new one. This interpretation is at least consistent, but I'm not sure whether it's correct or not.

rdl 13y ago
This seems slightly off somehow -- they were used to an aircraft where V1 was 80, were moving to one where it was 120. Event happened at 100; they were initially RTOing but were corrected by the grapevine to not RTO. That seems backwards from the behavior my mental model (which is what you stated as well) would want.
- pja 13y ago
  You're right. Given that V1 for a 777 is ~ 150 knots according to the online checklists I found I'm not sure what's going on either! If V1 if 150 knots then a warning at 100 knots should trigger an abort surely? Perhaps the point is that an Aft Cargo Bay warning isn't sufficient reason to risk aborting the take-off (which presumably carries it's own risks). So the warning alarm would go off & the pilots would abort because they were used to having such minor alarms being disabled about 80knots on their previous aircraft, therefore any alarm at speeds > 80 knots but < V1 is would previously have been cause to abort but on the new aircraft this was no longer the case. Makes sense? (Although personally I'd have thought that an open cargo bay door would be reason enough to abort a take-off - so that bit doesn't make sense to me at all.)
  - Piskvorrr 13y ago
    Surprisingly enough, for most issues (barring such situations as the wings literally falling off ;)), it's safer to get in the air to buy yourself some time for analyzing the situation and deciding (even if it's "go around for an emergency landing") than trying to decide during takeoff.
    - mikeash 13y ago
      It's not too unusual for pilots to turn a minor problem into a major one by trying to fix the minor problem too aggressively. A cargo door opening would be a good example of this. It doesn't threaten the aircraft, so it should be ignored until the situation is calm enough that your attention isn't needed elsewhere. Prioritizing problems like this is a big part of pilot training. It's a little bit like spilling your coffee while merging onto an interstate in a car. Slamming on your brakes so you can take care of your coffee will likely make things worse. Instead, merge, get stabilized, then figure out what to do with the coffee.

by pja 13y ago

rdl 13y ago

This seems slightly off somehow -- they were used to an aircraft where V1 was 80, were moving to one where it was 120. Event happened at 100; they were initially RTOing but were corrected by the grapevine to not RTO. That seems backwards from the behavior my mental model (which is what you stated as well) would want.

pja 13y ago
You're right. Given that V1 for a 777 is ~ 150 knots according to the online checklists I found I'm not sure what's going on either! If V1 if 150 knots then a warning at 100 knots should trigger an abort surely? Perhaps the point is that an Aft Cargo Bay warning isn't sufficient reason to risk aborting the take-off (which presumably carries it's own risks). So the warning alarm would go off & the pilots would abort because they were used to having such minor alarms being disabled about 80knots on their previous aircraft, therefore any alarm at speeds > 80 knots but < V1 is would previously have been cause to abort but on the new aircraft this was no longer the case. Makes sense? (Although personally I'd have thought that an open cargo bay door would be reason enough to abort a take-off - so that bit doesn't make sense to me at all.)
- Piskvorrr 13y ago
  Surprisingly enough, for most issues (barring such situations as the wings literally falling off ;)), it's safer to get in the air to buy yourself some time for analyzing the situation and deciding (even if it's "go around for an emergency landing") than trying to decide during takeoff.
  - mikeash 13y ago
    It's not too unusual for pilots to turn a minor problem into a major one by trying to fix the minor problem too aggressively. A cargo door opening would be a good example of this. It doesn't threaten the aircraft, so it should be ignored until the situation is calm enough that your attention isn't needed elsewhere. Prioritizing problems like this is a big part of pilot training. It's a little bit like spilling your coffee while merging onto an interstate in a car. Slamming on your brakes so you can take care of your coffee will likely make things worse. Instead, merge, get stabilized, then figure out what to do with the coffee.