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Qlink B717 stick shaker events
PILOTS flying a Qantas regional service with more than 100 passengers wrestled with shaking joysticks warning of an aerodynamic stall during two botched landing attempts at Kalgoorlie after they unwittingly programmed the flight computers with wrong data. A slip-up by the captain, unnoticed by the co-pilot entering the data, meant the plane's weight was calculated to be almost 9.5 tonnes lighter than it really was, investigators from the Australian Transport Safety Bureau found. That mistake meant the settings for landing angle and speed were wrong for the task, twice triggering automated ''stick shaker'' warnings to alert pilots to an impending aerodynamic stall - when the plane is no longer aerodynamically stable and in danger of dropping from the sky. Advertisement: Story continues below The first stick shaker warnings triggered at 335 metres, and again during the second landing attempt at 106 metres, before pilots managed to land on a third attempt. But during the landing attempts the pilots had not identified the underlying reason why the plane was unstable, pitching and increasingly difficult to control - mistakenly attributing the shakes to air turbulence. ''In response to the stick shaker activations, the flight crew did not follow the prescribed stall recovery procedure and did not perform an immediate go around [aborted landings],'' investigators found. Investigators examining the incident, which occurred on a Boeing 717 flight from Perth under the banner of QantasLink operated by Cobham Aviation Services on October 13, 2010, found a lack of standard cross-checking routines let the data mistake slip through. Although ''well rested'', the captain, who made the initial weight mistake, ''had been subject to numerous [roster] changes that had made it difficult to manage his level of fatigue,'' investigators said. Read more: Pilots were warned plane could drop from sky |
Thank god the cadet was all over it!
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I'm definitely not going trying to turn this into a cadet v GA thing but...
The copilot held an ATPL(A) that was issued in 2007 and a 717 type rating that was issued in 2008. The copilot had a total of about 4,520 hours aeronautical experience, including about 1,800 hours on the 717. |
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On reading the report I might have been a bit quick to judge. It's seems they did not disregard the stick shaker, it is just that they didn't conduct a go-around as per the procedure, I suppose that can be forgotten in the heat of the moment.
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Originally Posted by Scamp Damp
Thank god the cadet was all over it!
Originally Posted by configFull
I'm definitely not going trying to turn this into a cadet v GA thing but...
The copilot held an ATPL(A) that was issued in 2007 and a 717 type rating that was issued in 2008. The copilot had a total of about 4,520 hours aeronautical experience, including about 1,800 hours on the 717. 1234567 |
Another opportunity for the "experts" to pontificate and the average pilot to learn from.
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Quantas Data Entry Error...Really?
Seen on AOL news/Huffington post, this has got to be sensationalist reporting to the max!
Qantas pilots enter wrong data, risk plane falling from sky - AOL Travel UK I'm only an engineer but fail to see how this would 1) happen and 2) be able to effect the aircraft to that extent? I'm sure someone will reeducate me if I'm wrong I don't imagine seeing the incident happening as reported but I can understand the HF issues with crew roster changes. |
I'm sure someone will reeducate me if I'm wrong |
You beat me by 2 minutes....as long as it lasts its QANTAS!!!!!
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Given the importance of all-up weight, why does it continue to be estimated? There's millions of dollars worth of landing gear slung under the aircraft, yet it doesn't contain something that measures the pressure being exerted by the thing above.
Question: Why wasn't the operation of the stick shaker affected by the data entry error? Or was it? (ie, it kicked in later than it would otherwise have.) |
Stick shaker is triggered by an actual approach to a stall, measured by airflow/aoa I believe, so is independent of any inputted data
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Why wasn't the operation of the stick shaker affected by the data entry error? Or was it? (ie, it kicked in later than it would otherwise have.) By setting a weight in the computer less than the the actual the crew would have been given Vap and VRef speeds (Approach and landing speeds) that where below those required to maintain an AOA less than the stall (or at least close enough to set off the stick shaker which occurs prior to a stall). Given the importance of all-up weight, why does it continue to be estimated? |
Does the B717 have a Stick Pusher like most other T-tail aircraft? If so, and the airspeed bled slower than the selected incorrect approach speeds the activation of a Stick Pusher close to the ground could have had tragic consequences.
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Given the importance of all-up weight, why does it continue to be estimated? In most cases an estimated weight will be within 1/2 tonne the actual (assuming they operate in a similar fashion to other parts of QLink), and for practicalities sake would have minimal difference on an aircraft of that size. |
or could go down the cheaper route with a bit of software to monitor the aircraft's acceleration (airspeed cf groundspeed) during the first 50 metres of the takeoff roll.
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Anulus Filler
You may point out the fact that Quantas is spelt Qantas in my post, but its from the AOL news link not my spelling! The point I think I was trying to make is that reporters can present information to the public that are untrue/poorly researched (if at all!). The report states the a/c weight input to the FMS as 9.5 tonnes.....not 9.5 tonnes lighter! The question I have is how this wasn't noticed with a longer acceleration to or higher V1, VR on take off and also would this dicrepancy have caused more of an issue with the calculation of the landing distance required? |
The question I have is how this wasn't noticed with a longer acceleration to or higher V1, VR on take off |
All the report says is that the error wasn't noticed at take-off because of the length of Perth's runway and "the design of the aircraft".
It looks as if the correct take-off weight was 55 tonnes, whereas the estimate was 9 tonnes less: 16% too low. That would have carried through into the calculation of the take-off velocity, but perhaps the pilot, with plenty of runway ahead, delayed rotation. Or the pilot might have sensed that the aircraft felt 'sluggish' and increased the thrust. Whatever, it was a potentially dangerous situation (What if the stickshaker activated just after the aircraft was airborn?) There's another thread that refers to an incident where the thrust settings were too low. Both the weight issue and the thrust issue could be addressed by 'Force = Mass x Acceleration'. This already happens by intuition, but perhaps the takeoff procedure could incorporate an airspeed check at, for example, 5 seconds after the thrust is applied. A 16% weight error (or a 16% thrust error) will result in a 16% reduction from the anticipated airspeed, prompting a manual increase in thrust to take off and a check of the weight estimate while in the air. |
A pilot should have an approximate idea of what his/her V2 & Vref for a given weight rather than rely solely on a FMC generated speed. If the FMC generated speed is different by more than a couple of knots the difference should be investigated & resolved. For example it may be that a different flap setting from normal is being used or it could be as in this case the FMC is giving duff gen because duff gen was inserted in the first place.
I'm not suggesting pilots should know all speeds for all weights but if an aircraft such as a B717 is operated regularly at weights that don't normally change that much then any abnormally low speed should be questioned. Surely if multiple legs are being operated over the same routes day in day out & the FMC throws up a speed which you don't very often see (if at all) you say "haven't seen that before what's going on" or whatever! Too much reliance on computers nowadays & not enough <thinking>. Isn't that what experience & airmanship is all about? My 2 cents :ugh: |
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