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I thought you might be interested in a helicopter crash AAIB/CAA reports
This is AAIB Bulletin 2/2009 page 92 about Eurocopter Squirrel G-CBHL crash in Lanark on 15sept2007
and this is what the CAA should have published, but did not, burying the SAFETY info in the very wordy depths of the Pilot Handbook, and NO CHANGE of the diagram:
NO mention in the wordy CAA follow up below, of displaying this Eurocopter chart with DANGER written clearly on it - just wordy something or other called servo whatnot..... which does NOT say DANGER!!! Follow?
Pilots are VISUAL believe it or not and you should communicate VISUALLY please - laywers sitting at their very very quiet desks with NO Sense of Danger, always use their words to declare themselves free of responsibility of anything - the CAA are NOT up to the JOB!!!
A UK AAIB and CAA cockup in MY view ...... see below for the Heathrow crash cockup too..... no justification of their conclusion relative to other possibilities....AND NO accusation of Boeing's on-aircraft recording system failure mid-air nor the whole question of why the pilot selected APU start mid air either.......
I had a short series of interesting emails with the ATSB over the fatigue nature of the Qantas Trent engine failure :
https://www.atsb.gov.au/publications/investigation_reports/2010/aair/ao-2010-089 download the pdf file, and go to pages 80-83 for photos of the fracture. They were friendly (we were discussing the smooth nature of the fatigue failure), not like with the UK AAIB as for
......their POOR reporting of several Incidents/Accidents, particularly the Heathrow crash in 2008 of a Boeing 777 whose RR Trent engines ran down almost simultaneously at the Airport Threshold after 6 minutes of descent - not on the Highway just before, due to the Pilot's good aircraft handling (lowered the nose to fly over the road, not drop onto it) not even recognised in the AAIB Report 1/2010 - AAIB have poor perceptions!
Overview suggests AAIB 1/2010 is merely documenting normal operation of aircraft - very little, if anything, about checking that this particular flight did perform as expected. Nowhere for example, is an electrical system diagram presented, so no way to logically confirm the minimalist conclusions. The electrical system in an aircraft Provides the Pilot with Instruments and Lighting......was he "blind" on finals? AND, are the traces actually telling the real story, or was the electrical system causing recording problems? Why did he select APU start on finals if he had electrics?
I conclude that Boeing had failed IN DESIGN to ensure the recording systems worked all the way down to total aircraft depower when on the ground. Let alone the whole aircraft perhaps - so much seems hidden in the AAIB report...... At least one recorder(see the traces below) FAILED mid-air!! Incredible stupidity.
UK AAIB did not explore anything other than a hypothetical unobservable problem - icing of a normally hot metal oil cooler, when the ice disappeared before the aircraft or engine fuel systems were moved off the crash site!
Why did Rescue Services turn off several switches in the cockpit before the AAIB got there - Rescue arrived just over a minute after the crash. Clearly aircraft had to be made safe, but is there no procedure as to what to record first? No comment in AAIB report. Arriving just over a minute after the crash, means I expect QAR (Quick Access Recorder) buffer to have continued working until electrical switch off, yet the report says the QAR went off line ......
........ 45 seconds before crash. Why? Nothing about the logic that powers it, merely a guess that the data buffering system has delayed the recordings by 45 seconds - coincidental or not there is nothing analysed in AAIB 1/2020 to support that declaration. Was it electrical busbars going offline? Did the cabin lights go off before the crash, declaring that? You have to guess that too - I was obviously searching for signs of electrical power failure - nothing said.
Why do they not display busbar voltages? If the Aircrew selected APU start, it was for a reason like no electrics (perhaps cockpit lights went out ? - did they?). Did they ask them? Did they check busbar voltages to see? What NH does the IDG (the electricity generator) go off line, leaving only the battery powering the aircraft? What logic drives the RAT (Ram Air Turbine) to deploy? That should provide electrics. Yet fundamentally this question must be answered to provide us all with the confidence that that Emergency System works properly.
If the NH goes below IDG generation speed, it will be below idle - hence NL cannot be 40%, it must be lower - this is why I have been so concerned about the recorded values of ....well several things presumably.
Do Airbus use the same busbar and RAT logic as Boeing - do they need to know anything about this crash? Again, not considered/nothing said.
NL (= N1) is virtually constant at 40% during final approach (as is EPR actual) - does busbar voltage dropout freeze the recorded NL or EPR (only, for others seem to be working - what does the electrical diagram tell you? NOT PUBLISHED)? If ice is causing fuel blockage, why does NL not drop further? Why was the blockage so "easy", that it maintained engine speed significantly above idle, and not higher or lower - on BOTH engines at 40% almost precisely? In itself that is VERY surprising! Nothing said. At 40% NL, NH (= N3, but not displayed in the AAIB 1/2010 report) is perhaps about 74% - should the engine have a Blow Off Valve open below 75% NH to prevent surge? Nothing said!! If the ice blockage was a once off sudden event (report not at all clear, but so I have heard since from the FAA), it had to be huge and take ages to melt, if it be the real cause - pipe diameters/restriction at oil cooler, not mentioned at all..... too many assumptions in the vague report!
The ECU control loop scale is too small to read off their chart - why did it go to "11" for three seconds, nearly two minutes before crash? What does that "11" mean? It was the first time that EPR Command and EPR Measured diverged, well before the crash landing, so is very important. Nothing said!!
Incidentally, one of my recommendations was to slightly stagger throttles on long descents at "idle" in future as a precaution, for that way you will probably avoid simultaneous shutdowns - nothing said.
To concentrate on AAIB 1/2010 fuel flow - what would you look at for an engine rundown : fuel starvation, which AAIB did conclude, but for almost only ONE reason, not the several that were a possibility, hardly discussed - so, how about fuel pump speed(= NH = N3)? Nothing said! They should have had that info from the Data Recorder, but decided not to tell us. Not just me, but CAA, FAA and EASA - all critical investigators of safety!
The BA38 crash 777's engines were both Rolls Royce three shafts - not P&W or GE two shafts, and three shaft fuel pumps rotate much faster at idle than two shafts - this is important, for fuel flow will reduce about the same amount at idle on all 3 engine types, but if fuel pump rpm is higher at a low fuel flow, the fuel will be churned a lot more by the gear pump, such as to cause increased temperature and possible vapour bubbling - engines cannot run on bubbles!
And, were the fuel tank contents gauges showing plenty of fuel when they should have been showing zero? Nothing said!
Given the NOT available (NH = N3) rpm data, CAA, FAA and EASA would have been able to have a discussion/audit of the conclusions........ I saw no sign of such discussions....
What independence of mind did AAIB develop during the investigation - did they ask BAE Systems to help them think this through? I presume they had nothing to do with the aircraft or its design. Nothing said!
The engine ECU (control electronics and software) were apparently NOT AT ALL Checked - they actually over-wrote the Flight Software by Test Software it appears, so had no NO IDEA how in-flight reactions were doing - for example, the AAIB 1/2010 Data plots showed that the Software said the engines went into surge - was that Software working correctly? No Idea, for they never checked it! It is quite possible that they were not in surge of course (both engines at the same time maybe unlikely (unless high AoA!), but both fuel flows dropping to zero unlikely too (unless tanks run dry!) .......how do you know if you never check?
AAIB did not even report what the Pilots might have said about surge - never asked presumably!, AND Accident Investigations MUST surely be as certain as they can be that the Conclusions and Recommendations for the future are as near certain as possible.
Note : AAIB 1/2010 has 27 pages of fuel icing thinking and testing. Very many more pages than any other single item.
And their Engine Fuel System Diagram IS a DISASTER - this is AAIB 1/2010 :
This is mine, taken from the descriptions within the report, and for which I have no prior knowledge, other than my general knowledge of engine control systems - You will observe that the fuel pumps are driven by HP spool speed NH (called N3 in the report), but there is no sign of NH on the traces supplied in the report (only N1 which does not drive the fuel pumps !! And the throttle controls NH, not NL...) and which I reproduce below : I consider this a Criminal Omission.
Thus my Trent Engine Fuel System diagram, given all the several descriptions in AAIB 1/2010 (I had/have no pre knowledge of the Trent), noting that I have given you Questions (not answered in AAIB 1/2010) about the ECU's Affects too (Electronic Control Unit - which includes the Software). Also I supply info about Compressor Air-bleeds (Offtakes) which directly help prevent surge, and also driven by the ECU (questioning the surge indication on the trace below, from the ECU, it would have been useful to see what the ECU would have done with the info - open bleed valves?
No Logic Diagram to help understand - to question!) : ACOC - Air Cooled Oil Cooler, FCOC Fuel Cooled Oil Cooler (the latter iced up reducing fuel flow according to RR/AAIB, noting that that ice melted before any engine parts were inspected, and the Oil was surely warm at 85C at least, for ACOC cooling is limited at ground level and idle.....).
The traces of the last couple of minutes of BA38's flight would not print directly from the report except at very small scale (why?), so I magnified them on my laptop and took photos of that AAIB 1/2010 page 50, fig 20 as below, but then displayed top, middle and bottom of that page to ensure you could read it :
The engine rundown problem (which on BA38 was to a stable 40% NL (N1) - on BOTH engines surprisingly - and thus above idle - a recorder failure to record, just frozen at the last value indicated?) has not recurred to my knowledge, apart? from the one NTSB investigation they mention in the report...... The whole AAIB 1/2010 report is suspicious in its LACK of Multiple Detailed Thinking......
Below is a 26th June 2024 comment about what I see in those traces on Pilot Flying behaviour, which I had not done before. I obviously had those traces back in 2010, but I was commenting upon the engine behaviour back then :
The Pilot first noticed something was wrong 38 sec before crash impact, when he noticed the airspeed (at 130 kts) dropping below expectation, so Auto-throttled up, but then sudden retraction at 26 secs before impact (STAR this discussion to below)
and concentrating on Flying (always the First Priority), correcting a bit of left Roll and watching pitch attitude (AoA increasing thro 4 degrees), before slow throttling back up (why so slow?)
reduce flaps 30 to 25 degrees reducing drag at 16 secs (AoA 8 degrees), 110 kts, 0.5 mile before impact, anticipating possible on-Highway crash to avoid,
stick shaker (this is an "approaching stall" warning that airspeed is too low, and "stalled" the wing will not provide lift - stall will result in a sudden, perhaps big, drop in altitude, and it also tells the pilot to increase airspeed - so put the nose down and drop for a while until airspeed recovery) at 12 secs (AoA 14 degrees), 0.4 mile before
and finally nose drop (to AoA 8 degrees) 0.23 mile (375 metres) before, to reduce lift I think (so "Glide" onto grass, hoping to reduce human spinal SlamType-Drop damage - the sort of thing a stall would result in) having cleared the highway at that point, 7 sec before impact .....
.........thus the Pilot was good at his job A !
STAR : AAIB say engines "Auto-throttled" suddenly back at 26 secs, at only 120 kts - why ever should That (or Pilot !) throttle back happen when airspeed is so low? And then so slowly throttle back up? In total, 7 secs below max..... I imagine a Pilot would want to recheck throttle response, but throttle movement is very slow for that - he would have to wait a couple of secs to see rpm change, because the Control System would limit rate of rpm change, but the Pilot could move the throttle in a half second safely. And in any case - airspeed dropping low is not normally a time to throttle back, unless to reset something, but quickly surely.....
Paragraph 1.6.3.2 is ridiculously short of THOUGHT about this throttle back ! The Safety Importance is for another 777 aircraft, when the ground is close with low airspeed perhaps a little higher than this BA38 was. NO Logic Diagram or Description anywhere to help understand why this throttle retraction occurred.
Harassment of AAIB by JQ? MUCH MORE NEEDED do you think......
Does my audit help you (CAA, FAA and EASA) ASK Questions about how the whole thing might have happened in this 2008 crash ? Or wonder whatever was going on in AAIB...?
Jim
onto blog 24th June 2024, traces 27th June 2024, but 2010 letters to AAIB (Police obviously), RR, Boeing, and including some Operator's : British Airways, Qantas, Air France, Lufthansa Chief Pilots all, as best I can remember - about staggered throttles on long descents at idle too (one just above idle, the other at idle).
