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Originally posted by Gabriel
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This wasn't a procedure in our company.
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That's my assumption as well.
This wasn't a procedure in our company.
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A little more info from the interim report
(annotated by me)
Boeing B777-32WER registration marks PT-MUG was scheduled to fly from Malpensa (Italy; ICAO code: LIMC) to Sao Paulo (Brazil; ICAO code: SBGR)
[Not super-long-haul for a 777, but longish flight for sure]
Total of 398 people on board.
[Sounds about fully booked]
The flight crew consisted of the instructor captain sitting in the right seat and PF (pilot flying) for the leg, the captain-in-training as PM (pilot monitoring) in the left seat and the relief captain sitting on the jump seat.
[Good thing that they had 3 captains, including an instructor!]
Data on the FINAL LOAD SHEET:
- ZFW [zero fuel weight] 219460 [kg]
- TOW [take off weight] 328425 [kg]
- FUEL IN TANKS 109625 [kg].
The FDR data shows the following parameters entered in the TAKEOFF REF page of the FMS (flight management system):
- Flaps 5°
- Thrust 56°
- V1 [decision speed]145 kt
- VR [rotation speed]149 kt
- V2 156 kt
The performance calculation carried out with OTP [on board performance tool] by the operator after the event, considering the TOW to be 328425 kg, RWY35L, 30° OAT [outside ambient temperature] returned the following parameters:
- Flaps 5°.
- Thrust 38°.
- V1 173 kt.
- VR 181 kt.
- V2 186 kt.
[Did they enter the ZFW instead of the TOW for the take-off performance calculations? Did they "dyslexia" the first 2 digits and enter 238425 instead of 328425]
[Did they perform 2 independent calculations and compare them?]
[They knew it was a long flight, they knew they were full of people with their luggage, so they knew they were on the heavy side... Even without the independent calculations and cross-check, didn't the low ("737-ísh") V1/Vr/V2 call their attention? To any of the 3 captains?]
Take-off took place for RWY35L using the entire available runway (TORA [take off runway available] 3914 m, TODA [take off distance available] 3974 m, ASDA [accelerate stop distance available] 3914 m). [Note: Quite sure that "using" means that they departed from the threshold, not from an intersection, quite sure that they didn't actually USE the full length for lift-off]
[Good thing that they had a very long runway where, probably, even after setting a lower take-off thrust, they didn't extend the required take-off distance to a balanced-field length that was even close to the actual runway available, otherwise the outcome could have been much different]
Always referring to FDR data:
GW [gross weight] 328.2 tons,
109100 kg fuel on board;
[Very close to the dispatch numbers, so definitively a pilot screw up, not a dispatcher screw up]
11.25'59" the aircraft began its take-off run;
11:26'37" pitch up command was recorded with the start of the rotation at 153 kt [4 knots past Vr, nothing strange, I've seen pilots delaying the rotation for a tiny bit to get a more solid lift off, especially with a lot of runway ahead and both engines still running]
11:26'42" IAS=166 Kt, Pitch=8.2° Tail Strike Indicator 1 and 2 signals were activated.
11.26'49" the aircraft lifted off at an indicated speed of 180 kt. [That's 7 seconds of tail strike / scrape]
[The actual lift-off speed is reasonable, given that the correct Vr was 181 kts.
It took them 43 seconds to accelerate to 166kts (from 0 IAS, since the wind was about calm). That's 3.9 kts per second. Let me say that if they had been using the correct thrust they would have been accelerating at 5 kts per second (which is typical).
If they had started rotating a 181 kts and rotated at 3 deg per sec, they would have been at 191 kts by when they reached 6 degrees of pitch (2+ degrees short of tailstrike) and they would have lifted off normally.]
On RWY35L, a footprint was found on the ground (furrow with varying depths of up to 6 cm) of 723 linear meters
[So 7 seconds and 720m of scrapping the tail... nice! So how come that they were able to fly the plane, at 39000 ft, pressurized, just 2 days later?]
As a result of the occurrence, the aircraft suffered damage to the tail skid, a drain mast and the tail strike sensor.
[Ok, that explains it. I can't believe I am going to say this, but... Good job Boeing!!!]
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
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Is there no record of the actual weight values entered into the FMS?Originally posted by Gabriel View Post
I find this most baffling as well. Computed V1 was 36kts too low. Wouldn't that be a head-scratcher?[They knew it was a long flight, they knew they were full of people with their luggage, so they knew they were on the heavy side... Even without the independent calculations and cross-check, didn't the low ("737-ísh") V1/Vr/V2 call their attention? To any of the 3 captains?]
If they had started rotating a 181 kts and rotated at 3 deg per sec, they would have been at 191 kts by when they reached 6 degrees of pitch (2+ degrees short of tailstrike) and they would have lifted off normally.]
I assume this 777 did not have the tail strike protection system. With that installed, the tail strike protection command (TSP CMD ) is summed with the pilot’s input to form a total elevator command. But if the pilot pulls beyond 10deg it's inactive, so it can be overridden by tailstrike-inducing pitch commands.
None of this explains the tailstrike itself. If it won't fly at the low V1, they should just roll along until it does at a safe rotation pitch. But I take it your theory is that the pilots might have thought they were airborne (despite the lack of vertical speed or altimeter indications) and exceeded that safe rotation pitch value.
We have to be specific there.[Ok, that explains it. I can't believe I am going to say this, but... Good job 1990's pre-McNerney Boeing!!!]
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I can't help asking why, in 2024, gajillion-dollar airliners aren't weighing themselves, at least to cross-check pilot inputs and flag gross input errors. I realize the technology used on the L1011 was prone to getting quickly rattled out of calibration, but that was early 1970's tech. And I would expect a modern solution to be a fairly practical retrofit for existing aircraft with an FMS.Comment
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None mentioned in the preliminary report at least.Originally posted by Evan View Post
That's not my theory. My theory is (or was at some point) that at Vr the pilots just initiate a rotation at a prescribed rate aiming for 15 degrees. They don't stop to analyze at what point the plane becomes airborne, because they have no good indication of such thing (since the static probe in near the nose, altimeter and VSI -but not radalt- start to increase with rotation with the wheels still on the ground).None of this explains the tailstrike itself. If it won't fly at the low V1, they should just roll along until it does at a safe rotation pitch. But I take it your theory is that the pilots might have thought they were airborne (despite the lack of vertical speed or altimeter indications) and exceeded that safe rotation pitch value.
And I don't agree with putting the focus on techniques to avoid a tailstrike. All the effort should rather be put on techniques, tools, technologies, whatever to prevent low acceleration and low target Vr's. That is, prevent that the plane will actually lift off hundreds iof not thousands of feet beyond the poitn where it was calculated that it would. Because the runway may not be hundreds or thousands of feet longer than calculated. If this was a shorter runway then a technique to avoid tailtrsike may have helped prevent a tailstrike but not a wallstrike, fencestrike, or ILSantennastrike. You better got Vr correct and the power setting correct. Then the plane will lift off, with a proper rotation initiated at the proper Vr, without striking the tail, every single time.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---Comment
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It is worse than that. You (and the plane, and the 3 captains) missed something much more basic:Originally posted by Evan View Post
The plane knew its weight accurately and informed it to the FDR.The FDR data shows the following parameters entered in the TAKEOFF REF page of the FMS (flight management system):
- Flaps 5°
- Thrust 56°
- V1 [decision speed]145 kt
- VR [rotation speed]149 kt
- V2 156 kt
Always referring to FDR data:
GW [gross weight] 328.2 tons,
109100 kg fuel on board;
The plane knew the speed at which the pilots were intending to rotate.
The plane did not crosscheck these 2 pieces of data that it had available.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---Comment
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I don't understand the meaning of 'Always referring to FDR data'. How did it know the zero-fuel weight?Originally posted by Gabriel View Post
I think you’re right that the main focus should be on the Vr and FMS input errors but not entirely. This incident needed two errors: the wrong Vr and the wrong rotation technique. Boeing has developed a system for the latter issue but it is not installed on all their aircraft (including this one, it seems).And I don't agree with putting the focus on techniques to avoid a tailstrike. All the effort should rather be put on techniques, tools, technologies, whatever to prevent low acceleration and low target Vr's.Comment
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AirweighsTM system on newer B777F aircraft:
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Originally posted by Evan View PostWas this finally implemented and put in service?Tuesday, 27 March 2007
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---Comment
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No idea. It was 'selected' in the design spec but I cannot find any more information on it, other than that it might be a wireless system. 14 years after the Boeing selection of this system, I don't see any mention of it on any other Boeing or other airframe.Originally posted by Gabriel View Post
BTW: Why can't I upload ANY images anymore. I keep getting an error message. It's been like this for months. Can you upload images?
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