A China Airlines pilot unintentionally tried aerobatics in a 747. The aircraft barely survived up to 5g and many of the crew and passengers were injured. I saw an air crash investigation of this tonight, and I hadn't heard about it before. At the time, the autopilot on the 747 didn't operate the rudder. The failure of the pilot to engage the rudder when an engine failed resulted in the accident. The same program mentioned a fatal crash of a 757 caused by the maintenance crew taping over the pitot tubes.

That B757 mishap involves some interesting contributing factors regarding the cause that applies to all mishap reports. 'Cause' and 'contributing factors' can be confusing.

- Maintenance 'taped over the static ports' -- as properly required by the procedure. Apparently didn't un-tape 'em. (Yes, it's on every Maint checklist.)

- Post-maintenance QC inspectors did not discover the tape had not been removed afterwards. (Yes, it's on every PM/QC checklist. A maintenance event is not complete until QC is signed off and the acft returned to service by signature.)

- The flight crew did not discover the configuration error on pre-flight. (Yes, it's on every PF checklist).

- The flight crew did not properly execute the procedure(s) for static instrument error(s). Revert to power and attitude instruments per the EA checklist. A static system fault affects air speed, vertical speed* and altitude instruments in a predictable manner. [ One possible solution is to break the glass face of a *VSI to re-enable a functioning static pressure source. ]

- The flight crew did not maintain control of an otherwise controllable aircraft. (Fly power setting and pitch attitude. GPS ground and vertical speed and altitude today? ) (Hmm, how 'bout Air France Flt 447?)

So, what were the actual causes of that mishap? It's generally reported by the media and seen by the public as maintenance's fault.


Another thought: A Pilot in Command (PIC) is ultimately held responsible for the pre-flight condition of the aircraft. So, how does that work when the 'pilot' of a UAV is at a location remote from the launch site? An on-site QC-guy or Maint tech subs?

The 757 flight was at night time over ocean so the crew had no reference to the horizon. The tape was the cause, but in terms of the outcome, three people failed to spot the tape and the flight crew failed to safely return the aircraft to Lima. I'm not sure how they could have safely returned given the number of instrument failures.

In the case of Air France I believe that the pitot tube design was changed to try to prevent icing. How does the plane fly with blocked pitot tubes?



I guess they have a different rule for UAVs?

The static system has nothing to do with the directional and attitude gyros which provide pitch/attitude guidance, a stable heading reference and engine gauges. Associating engine thrust settings with speed, configuration and phase of flight is a required piloting skill true regardless of time of day or visual conditions.

I've just checked seven handy Pilot's Operating Handbooks (POHs) spanning the C-150 to the A320. Each has an Emergency Procedure for faulty pitot/static or Air Data Reference systems. That topic is also a critical item in all instrument flight training and checking events.

Procedures all call for seeking visual conditions using an appropriate thrust setting and gyro instrument guidance. (The A320 manual has three pages of configuration guidance covering all contingencies.) All include recall-from-memory items. Most acft without alternate static sources note that breaking the glass face of the VSI serves that purpose.

Detection, at the most basic level, is an inconsistency between attitude gyros, thrust setting and airspeed/altimeter instrument readings. Transport category acft normally also have a radar altimeter effective below ~2000' AGL.

Maintenance may be a contributing factor but failure to maintain control of the flight path of a (flyable) aircraft in this situation is on the flight crew and is the cause of the mishap.

Harsh words, but true.

OK, I'm trying to understand how the crew of the 757 could have overcome the warnings they were receiving. I read an article about breaking the vertical speed indicator. This provides alternate static pressure. I think the intention is to restore the operation of the altimeter? Presumably other instruments like the artificial horizon would still work, so they could determine the aircraft's attitude from that? I think you're saying that the crew should know appropriate thrust settings to approximate the speed, since with the pitot tubes blocked, the airspeed will never be known? Assuming night and cloud, would the next step be to find altitude to visually confirm the horizon? Then get ATC guidance to an airport with good visual conditions?


According to the TV program, the crew got overspeed then stall warnings, an inaccurate altitude reading from ATC which was based on the faulty reading from the 757 itself, and when they got terrain warnings despite being told that they were at 9000 feet, they didn't react soon enough to prevent hitting the water.

The trouble with breaking the glass on the VSI would be that yes it would give an alternate static pressure, but that would be cabin pressure which is from memory around 8,000 to 10,000 feet so it wouldn't necessarily work for other instruments. These pressure instruments have been around since not long after flying began, and basically come down to how much a copper bellows expands or contracts due to pressure differences. They are however supposed to be infallible which is why all the electronic doodads were always considered "advisory".

I wondered about that also. Fair enough in an unpressurised aircraft. But the bleed side of the pitot system is open? Presumably the reason that ATC said they were at 9000 feet was cabin pressure?

True, breaking glass is normally associated with un-pressurized, light acft. A 'complex' acft at altitude would have one or more alternate pitot/static systems.

Note that a cabin pressure differential (of 6 - 10K' delta-P) does not begin until above that MSL altitude so a pitot/static fault during the takeoff or approach phase would not be unduly affected.

Such alternate procedures are always situational and just one possible solution. A professional crew in a commercial acft should be able to cope -- and one never hears about those that do! Flying on power and attitude while troubleshooting is a given. Problems arise and metal bends when there's a lose of situational awareness.

Interesting that Airbus went for triple redundancy but Boeing did not. In the 757 case both tubes were taped over.


So why did the plane think that the aircraft was at 9000 feet when it was near sea level? That's odd.


In the 757 it seems that the pilots panicked and believed the ATC over their instruments. As you say, we don't generally hear about the situations where something went wrong but the situation was resolved without a disaster. On the other hand I have seen a few shows where a situation didn't end in disaster - like the Qantas A380 that made the emergency landing in Singapore. But yeah, generally you don't hear about it if the skills of the crew save the situation.

Way too much miss- and missing information involved, even in the 'official' mishap report, to have a meaningful discussion.

Wasn't the (pitot) 'tubes', it was the static ports and there are a total of six of 'em. Only the three on one side were recovered so condition of all ports is not confirmed.

And the 757 IS a triple system, as are all commercial jets - see stby insts. Takes three to validate a 'vote' against the bad guy.

The crew was going by what the ATC radar was reporting based up on the altitude encorder which was fed by the erroneous static system. The radar altimeter, effective below 1500', was the fail safe source and is not dependent upon the static system.

Even the reported instrument display errors aren't consistent with a complete static system blockage.

NEVER believe everything you read in the media about an acft mishap. Only the final report by responsible agencies - which may be hard to come by.

Aeroperu B757 Accident commentary

Actually all three sources including the standby instruments B757 charts

Sorry, I was thinking of the AOA sensors in the 737-max.


I thought I mentioned that the reading given by the ATC was erroneous. And yes, the radar altimeter was operative. The description in the article you linked was a little different to the video presentation (possibly because they wanted to make it dramatic). The article said that the pilot descended to 1500 ft to use the radar altimeter while returning to Lima, which would make sense. But they got a terrain warning from the computer. The ATC reported altitude made them think they were too high and they descended (despite the terrain warning and the radar altimeter) then dragged a wingtip. I don't understand why they would descend if the radar altimeter was working, but I think they got confused by the sheer number of alarms going on.

There's a repetitive mode to that issue. (e.g., Air France Flt 447) The heuristics and human factors involved in warning systems has improved but it's still got a long way to go. There's a big difference between being trained to operate an acft according to the POH and having the training and experience to deal with high stress emergency situations in the wild.

Military flt trng has an advantage here because one inherently and routinely trains to deal with intentional threats in a degraded acft while commercial training tends to rely on the 'Just follow the book if something breaks' formula.

Class D simulators have made a big difference in training for the real world and the assimilation of a CRM (Cockpit Resource Management) culture. This is an area prime for the integration of Artificial Intelligence (AI). The present Airbus ECAM and Boeing EICAS presentations are a step in the right direction but (IMO) tend to display too much unnecessary 'what's happening' info before presenting 'DO THIS NOW' instructions.

And it seems to me that the requirements for commercial pilots are being reduced on the basis of the level of automation in airliners, in order to ensure a stream of pilots available for an expanding industry (a situation which presumably is in reverse right now).


I imagine there's a lot more emphasis on basic flying skills. It reminds me of the situation of the "Gimli Glider" where you had an ex-military pilot who was able to save the aircraft due to his situational awareness and flying skills (I doubt that side-slipping a large unpowered commercial jet is part of standard training but I could be wrong).


I presume that simulators are in high demand right now with many pilots unable to fly. I've seen a lot of aircraft operating in Western Australia - it seemed more than usual, but perhaps it's because the number in the eastern states is so unusually low. It looked like the airlines were using the low infection rates in WA to keep their pilots and crews in the air on FIFO runs to mines.

You're absolutely correct.

Economics!! Simulator time is constrained by $$ and you certainly aren't gonna do it in an acft. Having a pilot off-line in training and allocating time in a $8-12M simulator is expensive -- training's definitively not counted as a profit center in the budget.

Economics directs that if a pilot meets the minimum passing requirement for a training or checking event you move on to the next event -- even when a second run through might be all that's needed to progress to real excellence in that task.

I instructed in B737 and A320 Class D SIMs for 18 years and worked in a Navy 'Top Gun-like' SIM environment for 2 1/2 years. Fantastic training advantages; you can train events you'd never consider attempting in an acft and repeat as needed -- and without taking a revenue producing asset out of service or risking it in training maneuvers -- especially if you can steal the extra-curricular SIM time.

And in every case, the best experience and confidence gained was when one could explore that extra 'what if' stuff. Imagine the confidence built given the opportunity to replicate Capt Sully's ditching or try a C-130 tactical 'whirl-pool' approach to a short-field landing in an A320.

Or explore a two-engine out drift-down to Lajes, Azores (Airtransat Flt 236) with time-outs to discuss options. How might that 757 crew have reacted if given the opportunity to experience a similar event and debrief it. Every serious mishap today is replicated in SIMs to learn everything possible from them.

(Ya know, PF's certainly a strange place to discuss this!)

I believe that the whirlpool approach was what the 747 freighters were using in and out of Baghdad? I'm not sure if it's still being done.


I think I've read of people simulating Sully's experience - actually it was certainly mentioned in the ATSB response where simulations showed that he could have made it back to the airfield, but that was by a flight crew who had already planned the engine-out landing, not a crew who didn't expect it. I am reminded of possibly apocryphal stories I have heard about an RAAF Mirage (A3-29) which made a dead-stick landing at a disused airstrip after a bird-strike - I was told that Dassault advised the RAAF never to attempt this again, and that the pilot's feat could not be replicated in a simulator. Apparently the Dassault advice was that the delta wing caused the aircraft to strike at the tail then pitch forward, breaking the nose and killing the pilot. I believe that as in the Gimli Glider instance, the RAAF pilot was also a glider pilot in his spare time.


But it's a chat group about aviation and thank you for sharing your knowledge and experience!

PS On the subject of the RAAF Mirage, as a very young child I travelled to Williamtown airport from Sydney with my uncle, and had the experience on the flight back of waiting for a while squadron of Mirages to land. Surprisingly, some of those aircraft could still be flying in Pakistan.