Originally Posted by
capngrog
I just saw the linked article in the Daily Digest of the Aviation Week Network.
The link:
https://aviationweek.com/commercial-...de9291345fa795
The problem seems to have been limited to overly shallow takeoff rotations from the high elevation environment of Bogota El Dorado Airport in Columbia. Could this problem be related to lack of side stick feedback feel while trying to avoid a tail strike? It would seem to me, given adequate airspeed etc., that it would be instinctive to apply whatever pitch was required to maximize climb and terrain/obstacle avoidance.
Cheers,
Grog
The report has a great use for cleaning buttocks post bowel movements.
The aircraft discussed in the report on the BEA website, which was delegated by the GRIAA to the country of manufacture, the BEA.... states that the aircraft achieved a threshold crossing height (DER) of 6', end of CWY at 20' and cleared the LLZ antenna obstacle thereafter by 12'. It specifically states a speed of V2+9 at that point.
OK. do the maths.
If the aircraft was compliant with the regulations by any stretch of the imagination, then with 3 engines it is required to achieve 35' for the end of the CWY, on 3 blenders, having suffered a complete power loss 1 second prior to V1. In the event data, there is no power loss. The target speed in flight is to achieve V2 by 35' [25.107(c)(1); 25.111(c)(2)]. In normal operations the flight crew are targeting V2 to V2+10 on all engines to ensure that at least V2 is achieved.
The reported event gets to achieve V2+9, and 12', 20' for the DER and CWY crossing in turn. If the rotate is at a low rate, then the speed will be high, and crossing heights are reduced, fair enough, but, the aircraft is within its normal speed range, has not had an engine failure and gets to... a dangerously low crossing height of an obstacle some 800' beyond the end of the CWY. The aircraft is imparted with a certain amount of thrust, and drag. The thrust is not linear, but is near enough for a rough assessment, and the drag is a function of rolling resistance and air flow resistance, which is reasonably easy to consider. Putting both thrust and drag together, and accounting for the rotate, the resultant acceleration curve starts off with a peak at relatively low speed, below 80KIAS, and which then decays at a reducing rate of reduction until rotate occurs, at which point the acceleration reduces towards but remains above 0 [due TAS change for constant KIAS target]. If you under rotate, and the energy was there in the first place, the result is a high speed trading off the altitude. So... how much altitude are we talking about? The aircraft had to be able to make 35' wheel height on all 4 engines (100%/115%), or 87% of the TODA, at V2. That means that the aircraft has to be higher without a failure when it gets to the end of TODA, by the time it takes to cross 13% of the TODA, at a rate of climb that occurs at a steady speed of V2, from 35' in the second segment. The rules give a mandatory requirement for the OEI case for gradient, and of course the aircraft actually has 4/3 or 133% of the thrust available to meet that gradient, so the rate of climb is considerably better in the all engine case [disregard the drag from an wind milling engine, rudder input, spoiler rise, aileron input etc... which all occur in the OEI case, reducing the all engine climb rate ]. The aircraft is endowed with a certain specific excess power [dh/dt], and if it is not used to achieve a climb, then that equates to acceleration, if it really exists.
So, we are to assume then that on all 4 engines, given that we are in fact at a lower drag point at V2+9 than at V2, the additional 9 KCAS that is within the normal tolerances of the aircraft.
NOTE: SRS [the manufacturers very own system design....] commands V2+10.... when on all engines, which is of course 1 KCAS higher than the speed that the unfortunate crew achieved and which are tacitly being admonished for by the BEA, and being professionally maligned for being the cause of the low crossing heights..
So... the white wash of the lack of performance attributes the causation to the flight crew, who are fully compliant with the design of the aircraft as certified, yet, the aircraft doesn't meet anywhere near the required clearance for safe flight. The clearance of the LLZ is about 3 diameters of a main wheel...
There are myriad reasons why an aircraft does not meet the certification requirement, density- humidity, actual air mass temperature at engine intake over the heat soaked runway.... wind variations, weight variations, and yes, pilot control technique. Of all of those, you will only see a low crossing and excessively high speed for the pilot technique case, and V2+9 at 12' RA, is not indicative of that case, the aircraft is about 25KCAS too slow at that point for this to have been due to the pilots under rotate.
Under rotate equates to excessive speed, so where is that speed when the crew are in fact 1 kt slower than the commanded speed of the SRS system, and are around 150-170' low on where they should have been to have complied with the rules. there is about 6 seconds of level flight gear up acceleration missing in the figures, and that shows that the specific excess thrust did not exist.
OEMs quote rotation rates that are not met in the real world, and which are alarming if undertaken. The A340 indicates the performance is based on achieving a pitch rate of over 3 degrees a second within 1.5 seconds of rotate commencement. The average in operation is much lower than that, achieving 1.75 degrees at about 2 seconds into the rotate. Any delay will increase the time to liftoff, but will have a commensurate increase in IAS at that point, and that is not evident in the performance of the aircraft; rotates are slow, but the speed is also not building up. It is necessary to get the attitude and speed outcome to achieve liftoff, the report appears to be quite silent on the speed that should have occurred given the slow rotate rate. The crew are targeting attitude rate and speed to achieve a safe liftoff, so it is not surprising that a lack of speed may give a slow rotate rate, and in this case, an inadequate rotate rate would have resulted in excessive speed, well above that recorded.
Stop bitching at pilots who are suffering from the lack of honesty in the performance figures, and start giving the SLF the performance margins that they are paying for and for which the industry has passively sat back and accepted the extent of BULL SH!T that is put into the PPMS.
I assure you that getting to 2' at the end of the runway when 427 people on your aircraft have paid to get to 185' is no pleasure, without a failure of an engine. The collective industry self denial at all levels, from the regulator, safety investigators, and airlines is demeaning.
Wake up and start smelling the colombian coffee.
For the pilot, don't expect any support from any level of your organisation, from the regulator, safety investigation body, airline or pilot union. Do learn your rights for single party taping, and comply completely with that and maintain evidence of your actions. Any party rocking the boat in a large corporation can reasonably expect to be victimised, the only question is how and when, not if. One example was an event where the crew assured data integrity, and completed independent stat decs during the flight, and took records of the resultant performance of the aircraft, which spoke directly as to causation. The data came back, and confirmed the high level of accuracy of the crews observations. The company suggested that the loading had been erroneous, yet the related cruise fuel burn penalty did not occur. The crew then asked for the company to look at other similar departures and get the data from those, and crew reports. That occurred some time later, and showed that out of a double handful of samples, none, (as in zero...) achieved better than the engine out performance. The crew in this case were asked to excuse a couple of samples as there was questions as to whether the aircraft had indeed got airborne on the grass or the concrete. Of the remainders, the majority were of a similar crossing height of the clearway as the reported event. At the end of the companies presentation of samples, none being safe or compliant, the crew was asked to agree that the samples showed no problem existed. This was in front of witnesses, with tape recordings, and copies of the samples provided. Good stuff. The national safety authority and the safety section of the regulator had all of the information provided under confidentiality, and oddly enough, the safety authority thereafter denied having any information on the matter, and then whitewashed the 15 odd events that they had information on. The deputy director of the safety authority while denying that they had any evidence of the event or events did unfortunately forward the data in a sealed envelope of their organisation, that remains sealed to this day, rather making the report of the authority, and the deputy directors formal statement to the govt ministry look shabby... The tape recordings of the meetings, and the data etc of these flights remain under lock and key.
Public safety is not enhanced by the usual response of organisations to staff that are fulfilling their reporting obligations under the law, and which may cause some inconvenience to assure the SLF of a level of safety.
JUST CULTURE is a hollow industry buzz word, that is not evident in the abuse of power that occurs on a routine basis to the crews. SLF pay for a standard of safety, and companies, regulators and oversight entities that abuse the messenger are paying a disservice to the industry.