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Precision Air crash, Lake Victoria

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Precision Air crash, Lake Victoria

Old 13th Nov 2022, 18:09
  #41 (permalink)  
 
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Originally Posted by Afrijet
this is the most unrealistic suggestion this year. In addition to flying the plane, the crew now have to unlock an armored door thatís designed to prevent cockpit intrusion. Not only disarm, but crack it open? While potentially operating to minimums in hard ifr. Will the door opener get out of their seat to accomplish this task?
I didnít say crack the door, just disarm it, not the biggest task in the world. Happened to an air India cores 737. Captain went for a leak, on his return the FO turned the heading knob instead disarming the cockpit door. The captain remained locked out of the flight deck and the aircraft went into a continuous bank and eventual spiral dive and ended up inverted. The plane was recovered by the FO and landed safely but must have been terrifying for crew and pax. Just from memory so donít quote me 100%. There is a distinct but rare chance the armoured door could get stuck locks in an emergency landing or fire in the cabin so why not open the cockpit locks during landing checks? Yes flight decks also have emergency ropes and escape hatches, depending on type, but having the main cockpit door available also adds a level of redundancy for escape from the cabin.
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Old 13th Nov 2022, 20:26
  #42 (permalink)  
 
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Originally Posted by MichaelOLearyGenius
Happened to an air India cores 737. Captain went for a leak, on his return the FO turned the heading knob instead disarming the cockpit door. The captain remained locked out of the flight deck and the aircraft went into a continuous bank and eventual spiral dive and ended up inverted. The plane was recovered by the FO and landed safely but must have been terrifying for crew and pax. Just from memory so donít quote me 100%.
That sounds like a very confused amalgam of several historical accidents.

If it happened as described, Air India did a very good job of keeping it quiet, given that you don't roll an airliner inverted without injuring passengers and/or crew.
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Old 13th Nov 2022, 20:43
  #43 (permalink)  
 
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I might be getting aircraft mixed up....but didn't the ATR have a kick out panel at the bottom of the door(could be a particular door manufacturer) in case the door is jammed or is it on a different aircraft type?

Either way, it seemed like a good idea.
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Old 18th Mar 2023, 19:22
  #44 (permalink)  
 
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The Aviation Herald has details of the preliminary report, which seems to have been issued recently. https://avherald.com/h?article=500a5725&opt=0
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Old 19th Mar 2023, 11:02
  #45 (permalink)  
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Here is the link to the report : report

Main points , attempting to land well below minima in VFR ( that we knew) , Captain (PF) was the chief pilot of the airline , 64, paired with a 45 years old F/O , CPL with 2000h ..ignoring GPWS calls...continuing descending with 1500 ft/min.

A question for the techies,: the props were in "almost feathered positon" , due to the impact ?
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Old 19th Mar 2023, 14:57
  #46 (permalink)  
 
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A question for the techies,: the props were in "almost feathered positon" , due to the impact ?
Could be.

Or it could be they were set that way (either by the pilots, or an automated NTS system) to avoid "negative torque." Very roughly and oversimplified, an analog to "engine braking" in a piston engine - the prop (or vehicle wheels) driving the engine, instead the other 'way around, at low power/throttle settings and higher airspeeds. The reduction gearing in TP's (which converts turbine rpms of 10000-20000 to prop revs of 1500-2000) "doesn't like" being driven front-to-back (negative torque).

Moving the pitch of the prop blades towards 90į (feathered) reduces how much backwards torque is applied to the engine shafts and reduction gears, from the prop spinning in a high-speed slipstream like a child's pinwheel in the breeze.

https://skybrary.aero/articles/negat...ing-nts-system

Negative torque can be produced by any low-power condition in the turbine - sometimes an actual engine failure, but also simply low throttle/power-lever settings. And the specific effects and limits can be different for different specific engine types.

Bottom line - there are limits to how much power can be reduced in a TP engine if one is trying to get down quickly at a high airspeed, by reducing power (fuel flow). The reason TPs have "flight idle" and "ground idle" settings.
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Old 21st Mar 2023, 06:27
  #47 (permalink)  
 
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Modern free turbine turboprops don't have NTS protection as such. The ATR has overspeed protection through the PEC which will eventually flame out the engine eventually if a certain RPM is reached. That is it just moves the blade angle coarser until it reaches the high pitch stops (78ish degrees) and then prop RPM will increase until the overspeed protection kicks in. More likely the near feathered prop feathered when it hit the water and failed, or the impact at high rpm forced it there, the other prop would not feather as part of the autofeather logic as that engine impacted and failed hence it was half travel or so.

At the speed this ATR was travelling as well as being configured the prop would be well within the normal operating range.

Because of this during fault finding you should be setting a low torque above flight idle position to simulate zero thrust if its not an actual failure, otherwise the prop will generate a lot of drag from 'windmilling'.
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