Citation Citation doing 6 360 rolls above Leeds
 

Summary of the Cessna 525A Citation CJ2 flight (Source; AAIB):



Synopsis
As the aircraft approached its cruising altitude of FL430, the pilot was not monitoring the indicated airspeed and the aircraft stalled, departing from controlled flight in a series of five 360° rolls to the right. The pilot briefly regained control before the aircraft stalled again and in the following recovery, the aircraft’s wings were damaged in overload. The pilot made a successful landing and examination of the aircraft’s recorded data revealed that the angle of attack (AOA) sensing system had ‘stuck’ in flight and the aircraft’s stall warning system
did not operate prior to the stall onset. Two Safety Recommendations are made, relating to the continued airworthiness of the AOA sensing system.

Full report attached - fascinating reading with photos of the wing damage due to "higher" G loads than expected - an unintended "almost ultimate loads test" ;-)

Everything ended fine, BTW.

Regards

Grunf

The aeroplane was a bit sick though.

Why wasn't the pilot monitoring the indicated airspeed?

Lol, because he is a human being that might not be perfect ? :)

Highlights the danger of climbing in VS mode especially at high alittude and especially single pilot.
That pilot examining high level wind charts at a crucial point approaching his cruise level was the deal breaker.

IAS mode is far safer as at least it will protect the pilot from getting to slow.

Never understood why this pilot diverted back into Leeds when he had a massive flat runway with a major Citation service centre in Doncaster.

Leeds is know for its altitude, low cloud, strong winds, poor visibility, undulating runway and down draughts while from his direction Doncaster was closer and far better on a number of counts for a diversion.

Pace

I am a firm advocate of climbing in IAS/Mach for this very reason. All I get from my crewmates however is resistance. "It's not necessary and it's uncomfortable for the pax."
All you need is a reduced speed climb in VS and then hit a high level inversion and it can all go pear shaped very quickly.

I've lost count of the times that's been said to me. It's nonsense. It's not uncomfortable for the passengers at all - and even if it were, the chances are that most pax would prefer it to the prospect of six 360º rolls above Leeds.

The unrestrained dogs bouncing around the cabin would have been 'interesting'.Fortunately they were none the worse after the event(s).

Why do you need to draw everything in black and white? Allow some shades of grey and it will still stay safe: you can safely climb a plane in VS-mode, if you continuously monitor all the parameters, because YOU are now the "IAS-mode" that will have to adjust the aircraft's VS. If you get distracted or need to something else, switch back to IAS-hold and it will stay safe. Simplez!

EMS

IAS has to be safer although I agree its not so comfortable as the jet will hunt the speed adjusting the climb rate etc.
I used to use VS but now use VS in descent only and IAS in climb so if you are 100% monitoring things VS is OK and in some ways preferable especially coaxing a climb at high altitude but then you have to be very disciplined.
I am sure that the pilot of this plane made hundreds of flights with no problems and it only takes one lapse of concentration or distraction for this to happen especially in a single pilot operated aircraft.

Pace

VS our IAS are techniques..; the safest being always the best, IAS wins... Now, we have other constraints dictated by the less performer. The less performer in this case is a combination of ATC and TCAS.

In order to "smooth" the side-effects of a regulation, the same regulators requested to limit the ROC on the last thousand , and even at 1500 before. Where in IAS mode requires to reduce the power to have this immediate effect, in VS, the thumbwheel makes people feel that they are in control, then they reduce the power in order to maintain the proper L/D, by reducing the speed. With AT, it becomes less a problem at LOW LEVELS, but if going to the first available ceiling, this habit may drive some in the same adventure as this poor Citation.

In my former company we had at least two instances of near stall ( the airplane has hi and lo speed prot, and eventually sorts itself out). but at FL410 when you have " increase speed" , "increase speed" this resumes that the least trusted items on the plane had gone south..

Speeds modes are always the best, just need an open mind to understand them.