View Full Version : B777 - Stop or Go??
Plank Cap
17th Apr 2006, 15:31
Just trawling for some info gents from those more enlightened, wise and experienced than myself.
According to the B777 QRH, the reasons to reject at the high speed end (80kt- V1) of the take off are stated as 1) fire or fire warning 2) engine failure 3) predictive windshear warning and 4) if the aircraft is unsafe or unable to fly.
The aircraft has a take off configuration warning system that will generate a master warning red light and aural on the take off for: any door not locked closed, take off flaps not set, main gear steering not locked, parking brake not set, rudder trim not within 2 units of zero, speed brake lever not down or stabilizer trim not in the green band.
My first question is would you deduce that it is accurate to say that a take off (at the high speed end) will be rejected for any master red warning light and aural? My second question is if you answer yes to the first one, why do Boeing see fit not to put this in writing?
hetfield
17th Apr 2006, 15:38
parking brake not set?
Ooops
False Capture
17th Apr 2006, 17:24
Depends on the airline. We stop for 5 main items:
1. Any fire
2. Engine failure (identified by 2 or more parameters)
3. Configuration warning
4. "Monitor radar display" warning
5. "Windshear ahead" warning
Answer 1: Yes
Answer 2: They don't need to as the very nature of the configuration warning means the aircraft is unsafe or unable to fly. In which case they have covered themselves with their fourth reason to reject between 80kts and V1.
Daysleeper
17th Apr 2006, 18:37
In most situations the config warning would sound as soon as the thrust levers are advanced. Thus the chances of it "going off" above 80kts are slight.
Have you considered which warnings are supressed above 80kts for your type?
BuzzBox
18th Apr 2006, 00:49
I agree with False Capture's reply.
As an aside, it's interesting to note that Boeing issued an SB earlier this year in response to several reports of spurious CONFIG GEAR STEERING warnings that resulted in RTOs above 80 knots. They did some tests and concluded that it is acceptable to continue the take-off if a main gear steering actuator becomes unlocked. The SB installs new software that inihibits the CONFIG GEAR STEERING message above 80 knots.
Plank Cap
18th Apr 2006, 02:27
Gents, thank you all for your replies. Well done to hetfield who correctly spelt out my error - should have been "parking brake set" in the original posting.
Buzz Box, I would be interested if you could point me in the direction of any further info re. Boeing's tests on the main gear steering unlocked scenario.
As a progression to this, would you choose to reject for the parking brake set master warning at let's say, five to ten knots below V1, assuming no other abnormal indications?
BuzzBox
18th Apr 2006, 05:25
Plank Cap,
Sorry, I don't have any further info about the tests, other than what it says in the SB:
"Boeing analyzed the RTO events and performed simulator tests, and concluded that it is acceptable to continue the takeoff roll if a main gear steering actuator becomes unlocked at a speed between 80 knots and V1."
As a progression to this, would you choose to reject for the parking brake set master warning at let's say, five to ten knots below V1, assuming no other abnormal indications?
No, I wouldn't reject the take-off in that situation. At that speed, it's more than likely a spurious warning - If the park brake really was set, the warning should have happened as soon as the thrust levers were advanced for take-off. I would suggest the chance of there being a real problem is very remote and that there would be a much greater risk of rejecting the take-off at high speed and stuffing it up.
Bolty McBolt
18th Apr 2006, 05:34
Buzz box
With your 777 fleet you mention you may continue T/O if gear steering (msg)becomes unlocked at a speed between 80 knots and V1.
Will the gear still retract? (I am guessing here) As boeing may have proved that its safer to takoff go around and land in this config??
On the 777
You wouldn't get a master caution light or aural warning for the park brake at V1 -10. The Master caution lights, aural warning and advisory messages are inhibited from 80kts to 400 ft or 20 secs after rotation.
Config warnings are all going to come up prior to 80kts
If it were possible ... A park brake message at V1 -10 is definitely a go in my book unless it was associated with application of the brakes resulting in rapid deceleration
Plank Cap
18th Apr 2006, 11:41
Buzz Box, thanks for your continued input and the quote from the 777 SB regarding main gear steering. I notice you would NOT reject a high speed take off in the instance of getting a config warning for 'parking brake set' shortly before V1. As Boeing have said on record, there are times when spurious warnings occur. I entirely agree with the GO call in this event, assuming I had the brain capacity to work it out at that stage! Either way, a decision has to be made.
The interesting thing here is that we are now saying that even in the event of receiving a Master Warning red light and associated aural, there MAY be occaisions when the safest course of action is to continue the take off. This is how I previously understood life to be in the Boeing philosophy........
Plank Cap
18th Apr 2006, 11:52
BGQ, welcome to the discussion. I agree with your statement re. the Master CAUTION inhibit. Can't speak for your airline's aircraft, but with ours the Take Off Configuration is NOT inhibited until V1. One of the items it will trigger for is Parking Brake Set with associated Master WARNING red light and aural.
I agree the system should alert you at the early stage of things being wrong with the application of take off thrust, but there are documented cases where it has not triggered until very close to V1, some spurious, some actual.
BuzzBox
18th Apr 2006, 12:22
Bolty McB:
Will the gear still retract? (I am guessing here) As boeing may have proved that its safer to takoff go around and land in this config??
To my knowledge, the gear will still retract. The manuals are a bit vague, but barring a hydraulic malfunction or door sequencing problem the only thing that will stop the gear retracting is the landing gear lever lock solenoid failing to release. As far as I can tell, the landing gear lever lock solenoid is controlled by air/ground sensing, nothing else.
Even if the gear lever is stuck down, the QRH only says to push the override switch and move the gear lever to up. It says nothing about checking for other gear malfunctions, unlike the 744, where the override switch shouldn't be pushed in the event of a GEAR TILT or BODY GEAR STEERING message. I'm no expert, but it sounds to me that Boeing don't think there's a problem raising the 777 gear with the main gear steering unlocked. There's nothing in the SB or Ops Bulletins that would suggest otherwise.
BGQ:
You wouldn't get a master caution light or aural warning for the park brake at V1 -10. The Master caution lights, aural warning and advisory messages are inhibited from 80kts to 400 ft or 20 secs after rotation.
Perhaps it's different on your aircraft, but on ours the master CAUTION lights & beeper are inhibited from 80 knots to 800 ft RA, or 30 secs after lift-off. The master WARNING lights & bell on the other hand, are inhibited from V1 until 400 ft RA or 25 secs after the inhibit began. The take-off config WARNING (which is triggered by a number of conditions, including parking brake set) is not inhibited until V1.
Buzz box you are right.... the config warning is not inhibited until V1.