I was unclear on his example -- their manual says to ignore "aft cargo door" cautions during takeoff? Are those known to be false-positives, or just not that important? I thought the cargo doors were structural parts of the aircraft, and thus having them open would cause both structural and aerodynamic problems. Maybe they just continue takeoff and land again?
In modern planes there is a filter on the warning computer that doesn´t allow to show certain non vital failures between 80 knots (or 100 depending the plane) and V1. For example an engine fire is going to trigger the alarm, but not an engine EGT (exhaust gas temp) over limit. But the list of warnings not shown, and the ones shown but that must be ignored, are different from plane to plane. That´s why this instructor was doing this test, to make them learn that the 777 had a different list and requirements from the previous one. Mind you that after you´ve been in 2 or 3 different planes it´s easy to react automatically but with the previous plane list.
It´s known that pilots are oversensitive to warnings during take off. A rejected take off is a dangerous maneuver that must be avoided if unnecessary, and is trained in each simulator session. This is more important in wide body airliners like the 747, 777, A340 or A380, as their take off weight is so high that a RTO (rejected take off) will blowout some tires (of the main landing gear) due to the stress or the temperature increase inside the tire created by the brakes. Once the plane is stopped, it has to wait isolated at the taxiway because there are temperature plugs at the tires that may blow out, nobody can get close during that time. If the weight is too high they will even burn as the brakes will be white hot. Look at youtube for a certification RTO of a big plane to see it, or some brake energy absorption test at the laboratory, to see how much energy they have to mannage.
In this case(the simulator story) a after cargo door is one of those warnings that you have to ignore as the plane will flight without problems, then you may turn around and make a landing after dumping some fuel(to decrease the weight).
Hope this helps
Edit: some clarification
Below 80 it is possible to RTO without problems as the speed is still low. Once you reach V1 you will NEVER RTO! as this speed is calculated taking in to account the runway length, and in such a manner that if you RTO at V1, the runway remaining once you have stopped is just a couple dozen of meters.
The V1 is so high because that way, when you become airborne, you´ll have a better climb gradient even with an engine fail. All this stuff is calculated with an engine fail, after all it is the most important and probable fail you will encounter (the reverse deployment on take-off is much more severe but thankfully very very rare), and that will affect your climb capability.
An example of the braking test - stopping a 288 tonne 777 travelling at 200mph. The disc brakes were on fire, and they then had to taxi around on wheels at a temp of 3000 deg for five minutes to simulate the time it took for fire trucks to arrive.
As amazing as the 777 is, the 787 seems to be even better (and there's talk of updating the 777 with 787 technology).
I really hope next time they go shopping for Air Force One they take budget into consideration, and the end of the cold war, and ETOPS, and seriously consider a twin engine (ideally a 787 with a reduction in passengers, but probably they'd go with a 777 and continue taking way too many people.) Outside of cargo and the military, four engine passenger jets seem to be a dying species. (and obviously the A380 and other airbus products aren't in the running for AF1. I still haven't gotten a chance to fly on an A380.)
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.
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.
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.)
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.
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.
>I thought the cargo doors were structural parts of the aircraft, and thus having them open would cause both structural and aerodynamic problems.
I don't know about the other stuff, but I do know that the structure of an aircraft must not be designed to depend on something like a door being closed. That is, if the door is carrying load when closed, "you're doing it wrong". The door frame might carry load, but that wouldn't care whether the door is open.
Generally, something on an aircraft is either intended to carry structural load, or it's designed for such loads to bypass it entirely.
It would definitely hurt the aerodynamics for a door to fly open, but that would probably be a minor concern relative to the other hazards it introduces.
