I have reviewed the animation and audio;– not admitting to retaining a copy!
It would be unwise to form conclusions on the cause of this accident from this data as it is only a very small subset of that which would be required to gain a full understanding of the situation both before and at the time of the accident. However, IMHO there are questions which can be raised based on what is present / not present in the animation. The answers to these questions, or just the questions alone could be a catalyst for thought or even initiate valuable safety activities.
The animation starts on base leg, thus what the crew had deduced after the failure, their reactions/actions, and subsequent abnormal/pre-approach briefing is not known. Similarly, there is no data on any associated human factors or organizational issues (fatigue, tiredness, training, safety culture) which could have significant input to understanding the accident.
It is not possible to identify the speakers from the audio except where it might be assumed that the pilot flying (PF) calls for checklist and actions; up to five voices can be identified. Verbatim CVR quotes are avoided as these are normally regarded as personal and private.
Before turning final, ATC gives landing clearance and the PF calls for the landing checklist. Aircraft configuration: 175kts, 38 flap, eng 1/3/4 at 65% (# 2 eng throttle at ‘Idle’, N1 at 15%, assumed to be shut down).
There is additional (extraneous) discussion on anticipating hot brakes and no necessity to aim for a gentle landing – ‘think about clearing the runway/taxi’. An interpretation of the tone of this reminder was of an ‘instructor’ or mentor briefing a student or a senior pilot to a junior – alternatively it could have been a ‘self briefing’.
Who gave this briefing?
Was this an indicator of the crew’s interaction or culture (power/distance, cockpit gradient) or alternatively a positive reminder of issues to consider – good CRM?
Was there any history of the aircraft brake performance at heavy weight that could have influenced the crew – a previous incident?
What specific advice is there for an overweight landing – use restricted flap?
Should the crew have considered / could the aircraft dump fuel?
Was the discussion distracting at this stage of the flight?
The landing checklist items were run smoothly, but quite quickly; there was an item for EGPWS.
Does this suggest that the briefing was for a non normal flap selection requiring EGPWS to be switched off, or is this a C5 specific item (QFE ops, DME/FMS input only)?
Gear was selected down and checked, ‘flaps’ were called from the checklist, the flaps move to 90 deg. Electronic audio call of ‘1000ft to go’
What flap setting is required for an approach with an engine inoperative, when is it set – full flap vice restricted flap for heavy wt – was this a conflicting combination in this situation – engine out and heavy?
What, if any, differences are there between an engine out approach and a normal approach? If different, is there a specific checklist for the differences?
How often do crews practice with an inboard engine failed?
At 900 RA (4.5nm), the throttle positions retard to idle (N1 50%), 165kts for 146 kts (Vapp). As the throttles are advanced, #2 and #3 are interchanged, thus only Eng 1&4 provide thrust, 70% N1 becoming 90% or greater for the remainder of the flight. The animation shows eng 2 at 15% N1 (shutdown) and eng 3 at 30% N1 (idle), landing checklist complete - Rad Alt 700 – thus a relatively short time for all of the above to have occurred.
Who normally manages the throttles during an approach?
What rudder trim is set with an engine inoperative or is there any rudder bias system which will / will not provide any force cue from the rudder as to which engines were in use.
Was the engineer head up? What should he be monitoring his or the crew's instruments?
Discussion:- note the significant differences between aircraft variants in the display format of engine parameters. See
US Cockpits, search for ‘C5’; review the range of photos pre/post flight deck update including the engineers station; also see the C141 for comparison – a common ‘Lockheed’ flight deck?.
Of particular interest are
C5 Old flt deck and
New flight deck.
After the lessons learnt by civil regulators / operators from the FAA report
‘The Interfaces Between Flightcrews and Modern Flight Deck Systems’, it is surprising that so many potential error paths (design weaknesses) can be identified with in the C5 flight deck upgrade.
- The engine displays change from strip indications to dials (N.B. previous transport aircraft, C141 also has strip instruments).
- The secondary engine are displays positioned alongside the main dials without vertical correlation (recall the 737 Kegworth accident). Was the C5 engineer’s engine display changed to ‘glass/LCD’ strip or dials?
- Two sets of throttle levers; note the asymmetrical arrangement of the outboard levers.
- The inability to lock out an inoperative throttle lever – some civil aircraft have latched / combined levers and HP cocks.
- Strip airspeed and altitude appear to be on EFIS, but where are the ‘strip’ displays of AOA and Rad Alt located (assuming mechanical strip displays in the old flight deck).
How many simulators have been modified to the new flight deck standard?
The animation continues with discussion on ‘boxes’ and ‘speed’ apparently relating to the PFD, RA 6-500ft, 4-3.5nm: – “check speed now” – 148kts (for 146Vapp). The voice ‘chatter’ again appears to be ‘non normal’. The tone was explanatory, similar to an instructor or more knowledgeable pilot/crewmember explaining an aspect of the aircraft or display. Comment on the (EFIS?) ‘checkerboard’.
Supposition:- this point was probably the last chance of identifying and recovering the situation, thereafter there was insufficient height to dive to maintain speed and then raise the flaps, or speed was always too low to raise flaps. The only plausible recovery would have been the identification of the engine mix-up and applying full power.
RA 480ft, 138kts (Vapp -8), Eng 1&4 N1 95%. A call for ‘flaps 40 – no disregard’.
Was the cancellation in recognition of the low speed?
Was the focus of attention in this situation the drag / speed, but not thrust?
Was power ‘assumed’ to be max on Engs 1, (3) & 4.
What was the crew's understanding of the situation?
There were comments and discussion where the pilots were aware of the increasingly low approach. Background voices (independent discussion amongst other crewmembers?) were querying the flap setting, whether they should advise/question the pilot – they appeared to be unaware of the situation, the planned approach, SOPs, or the precise stage of flight.
At RA 210ft (Vapp –16) there is a movement of Eng 3 throttle lever to 30%, but without any noticeable change in N1.
Who moved the throttle lever, was it done consciously or subconsciously?
Did this indicate that someone had doubts about which engines were being used?
The short remainder of the animation and audio relates to being low and slow, except at 170RA (Vapp -18) there was a call from an indeterminate source to ‘get the flaps up’; flaps retracted to 40. The aircraft encountered stick shake; there was a stall warning before ‘touchdown’.
This review is not to find fault with any crewmember or make judgment on anyone’s responsibilities or actions; it is to seek a better understanding of what appears to be an accident of human error. The narrative above is provided to encourage others to explore the vast range of ‘what ifs’ and why didn’t … , and all those seemingly innocuous issues that should have been taken account of.
For those who have sought a single cause or unwittingly allocated blame in earlier posts, take time to reflect on the vast range of human factors that could have been present in this accident. Take time out for ‘Self Reflection’ – “it could happen to me”.
A detailed understanding of this accident might provide a good example of the difficulties of Threat and Error Management, whether it is conducted by an individual, the crew, operator, management, command, or even at regulatory/senate level.
An accident is a lesson to be learned. Detect and avoid, or alleviate those error provoking situations (foreseeable events) which can be identified beforehand so that whatever human capability remains can be used to counter
those unforeseeable diverse events such as those apparent in this accident.