N380CR AAIB Report
 

http://www.aaib.gov.uk/cms_resources.cfm?file=/Cessna%20525A%20Citation%20CJ2+%20N380CR%2001-15.pdf

Makes for some startling reading - 90° nose down, 115° Roll angles during the upset, and a peak of 4.5G in the recovery.

Some questions though for those of you flying the CJ2 - why do you climb in IAS not Mach at high altitude? That seems just to be making it harder. Would I be correct in thinking that very little of the type or recurrent training is done at high altitude?

Finally, are any of you involved in training owner-pilots? What sort of line oriented training do they get (insurer-mandated &c) if any? Is it just an annual LPC and that's it?

Excellent report on a nasty incident... AoA becoming a recurrent theme...

seems like the link is not working

Try this link;


Air Accidents Investigation: Cessna 525A Citation CJ2+, N380CR




coldair

It uses Collins Proline, so the display will transition from KTS to Mach automatically at altitude.

As for training, for certification a simulator need have no fidelity above 20,000' so it is correct to say that little or no training for all types occurs at high altitude.

Any mention of what colour the pilots underwear was following the 'successful landing' ??

I'm an enthusiast (at age 55 more wish I had been than wanabee!) not a pilot and perhaps should ask this question in Spotters but as it's relevant to this incident it makes sense here.

The report refers to an Angle of Attack sensing system which, together with pilot's use of a particular autopilot mode, was key to what went wrong. I'm struggling slightly with what such an instrument is showing and the 'units' in which it measures.

As I understand it angle of attack is determined by (a) wing incidence and (b) pitch. That doesn't need an instrument so presumably the gauge is showing something more complex computed from pitch but also other parameters including airspeed, air density/altitude, flap position etc. Is that right? If so what is the 'unit' being measured?

In practical terms is the key keeping it in 'green zone' by control of the parameters mentioned above?

Airbanda
 

Google AoA! Generally the angle between the wings effective chord (the shortest distance between the leading and trailing edges of the wing) and the relative airflow. Measured by externally mounted probes which vary in function by manufacturer. Augmented on some aircraft with acceleration sensors/data. It can get very elaborate.

Fundamentally, low airspeed requires an increase in this angle to maintain level flight. To reduce speed further requires additional lift, such as is provided by flaps or slats.

At higher altitudes, air density is reduced and it becomes manifestly important to limit AoA and protect speed, not allowing it (speed) to decrease below that required to ensure sufficient airflow over the wing to maintain level, or in this case, ascending flight.

If you approach the AoA in any flight regime at which the speed becomes insufficient to maintain the required lift, the sensor should provide sufficient warning to reduce the angle or increase speed. Certain aircraft have stick push systems, also triggered by this sensor, to reduce the angle should other cues be missed by the pilot.

At some point it is likely that Cessna informed all pilots passing through its facility about the risks of VS? Don't use it unless you are on it like a hawk at high alt or low speed!!

If the aircraft is not climbing in FLC/FLCH, tell ATC sooner rather than later and accept a short level segment until the temperature or weight drops. If eeking the last few feet out of it at TOC be mindful of accepting large heading changes from ATC, particularly if the ride is not smooth.

No shaker either, tho if it had gone off, assume the AP disconnects anyway?

Can't imagine how scary this trip was, very lucky not to pull the wings off. Citations, I imagine, do not enjoy the same load tolerance as L29's. All the same, got it back on the ground, and all the occupants safe.

Interesting that the pilot who was flying single crew had logged only 16 hrs in the previous 90 days / 5 hrs in the past month.. even assuming that these few hours were logged on type, allowing for 'chocks' times this is barely one hour per week. Not a regime that keeps one fully familiar and confident as single crew in a sophisticated aircraft.

The AAIB conclusion to this report "the pilot operated the aircraft in an autopilot mode which left it vulnerable to a stall..." seems vague in its intention at establishing an actual cause.

According to the report, on this aircraft type the pilot has two climbing/descending flight director (not autopilot) modes to choose from: Verticle Speed and Flight Level Change. Both, according to the report are acceptable means of achieving the job (according also to the AFM reference) and both are fully certified as safe for operational use. The pilot reported that in FLC the plane would hunt and this is the reason for using VS, presumably in VS the occupants had a smoother more consistent ride, or perhaps the pilot found it easier to comply with ATC Verticle speed requests by using VS on this day or previous. Perhaps the pilot found it easier to maintain the RVSM required 1000 feet per minute or less within 1500 foot of desired altitude (albeit above RVSM). It doesn't really matter in my opinion why the pilot chose to use a perfectly usable flight director mode to achieve the aim, the fact is that he/she failed to monitor the aircraft during a critical phase of flight. Verticle Speed and Flight Level Change are just proverbial tools in the tool box and neither is more dangerous than the other in an unmonitored aircraft. To cite the use of VS mode alone as the number one cause seems like deferring attention from the actual reason and that can only be non monitoring by the pilot, otherwise one could blame gear up landings on the act of retracting the gear in the first place, what a dangerous procedure retracting the gear would be if the pilot forgot to extend it again before landing due to destraction.

Slightly hypothesising here but in theory if the pilot were to climb in FLC at a fixed Mach number then, as the aircraft climbs the indicated airspeed (IAS)will reduce and the same result would have occurred (this presumes obviously that the aircraft would have an excess of thrust to maintain a given Mach Number to the target flight level, otherwise if unmonitored it would level off and possibly start descending!).

The AOA not working correctly was bad luck and didn't help the pilot by pre alerting the stall correctly but again, if the speed was being monitored then this situation would not have occured. All aircraft have a minimum drag speed (VIMD) which occures usually at the same approximate speeds for given conditions that the pilot should have been aware of. If the AOA indicator had been observed stuck reading .6 then a vigilant pilot would have noticed this not working and relied on his/her experience of this aircraft type to maintain a 'not lower than' speed. Flying below the VIMD is probably why the IAS kept dropping beyond what the pilot considered to be normal.

In my opinion, and it is just an opinion and not based on fact, either VS or FLC could have yielded this event and along with the AOA indicator were red herrings. This plane was clearly flying too high and too slow for the given conditions and the pilot took his/her eye off the ball.

I always thought the golden rule was NEVER use VS mode unless you are constantly monitoring IAS and preferably NEVER use it at all!

You would be amazed to find out that the vast majority of Citation pilots use VS during climb (some also use Pitch mode), at least in my experience.

It is also true that FLC works like crap and is really uncomfortable for crew and pax most of the time.

Each aircraft has a climb schedule speeds and above specific FL the climb should be on a specific Mach number.
If the pilot was maintaining the required Mach then the aircraft wouldn't have stalled...
Once he passed a specific AOA (which he wasn't aware of) due to the fact he was climbing at 1000ft/m at FL410!! and assuming he was leveling at that altitude it would have taken him quite some time to recover the speed but he was continuing with his climb and that led to the stall.
If he was keeping FLC .something that was giving him the protection...

Most CJ pilots climb in VS. Most CJ pilots are capable of monitoring the airspeed and adjusting the VS so that you stay at an appropriate speed for your weight/height/OAT. This accident happened because the pilot was a gimp and didn't monitor his airspeed. The incident could have been that he was climbing in FLC, the aircraft got too high to maintain the airspeed or went into an airmass with a significantly higher OAT and began to descend to maintain the speed and collided with other traffic - its got bog all to do with the mode he was climbing in and everything to do with basic piloting skills.

The CJ has straight wings and it doesn't climb at its cruise speed, its simply too draggy, and you sometimes accept fairly low climb rates to get to the cruise altitude you want. Once it gets there its quite happy and accelerates to its normal cruise speed reasonably easily - swept wing aircraft are much more prone to the "back of the drag curve" problem than a straight wing aircraft is. Being high in a CJ can be useful - you're slow so being "out of the way" can give you preferential routings, your fuel burn is substantially lower, and you're out of the weather which is a good plan in a little plane. But you need to monitor how you get there which this bloke didn't.

+1, even in the bigger ones like the C680 I´m flying now it does not work well. Climb through a temperature change and feel the A/P 'going wild'. Chases the bloody speed wildly. We mostly use VS - and monitor, But then we are 2 guys up front....

From memory (havent flown one for about 5 years) at ISA at max all up weight you could schedule 230kts/M.55 in a CJ and it would get you there as long as it was less than about ISA +5. Any more and it really struggled above FL410 but was fine at ISA. But if you did it in FLC it felt like you were on a childs rollercoaster. The Phenom was a lot better in FLC and I used it quite a lot, about 50% of the flights. The Challenger climbed well in in FLC and I used it almost all the time. The Global seems happiest in pitch (FPA) and we use that a lot for the majority of the climb although it bongs a caution at you when you use it if its a batch 3 aircraft. Doesnt matter which mode you use in my opinion, its a false idea to believe you are "protected" from stalling or descending unwittingly. You monitor the aircraft, even if you are drinking tea or fannying about on an iPad, and you watch for unpleasant trends developing on any of the tellys because thats what you are paid to do and if you cant do it you give up the job. I'm flying all the time, autopilot is helping me.

Tom

What an incredibly ignorant and judgemental post. Yes the pilot made huge errors, I'm particularly surprised at their lack of monitoring prior to levelling off, especially in the upper levels.

However the person didn't do it on purpose. I'd say they take their flying seriously given the fact they attend FSI every year. How many 'proper' CJ operators go to the expense of sending their pilots there annually? I'd be interested in the FSI philosophy on MCP selection. Any type I have attended FSI for has always recommended FLC/IAS. And actively discouraged VS. Indeed any type I've flown for any operator has actively discouraged it.

If the CJ is so marginal up at these levels it sounds to be as though it has no business being there. This has happened and been reported. How many close calls have there been that haven't been reported. Climbing in V/S is risky. There have been enough heavy jet transport incidents reported over the years to exemplify this. If FLC is uncomfortable for those in the back speak to the manufacturers, or get a better airplane.

Several types are practically unusable in FLC. You are right that climbing in VS near the edge of the performance envelope is risky, but pitch mode is an often neglected mode, which used sensibly, can offer a comfortable ride whilst not pitching you quickly into a stall like VS can. Not for nothing did Concorde cross the Atlantic in pitch mode the whole way.

The reason VS mode is frowned upon is because if not watched it could potentially lead to this exact scenario.

The fact still remains that the aircraft needs to be watched whatever climb mode is being used. Not paying attention when using FLC has the potential to lead to descent, and climbing in pitch mode can also lead to a stall.

There is no one climb mode that offers foolproof protection, and all three modes do have useful purposes.

Paying attention towards TOC is key. So too is understanding aircraft performance, and that climbing too high too soon is a waste of time and fuel.