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Old 19th May 2017, 02:24   #21 (permalink)
 
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Sheepy,

A lot of the difference in glide with a windmilling prop can be attributed to turbine vs piston. To turn over a piston engine that isn't running requires effort to compress the air on the compression stroke. A turbine engine like the PT6 is a lot easier to turn over because the free turbine does not compress the air in the engine.

The energy to turn the engine has to come from somewhere and it comes from the potential energy of the aircraft through a higher sink rate.
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Old 19th May 2017, 03:50   #22 (permalink)
 
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Reciprocal turnbacks can be a killer. Turning back to a cross runway is generally more achievable. Practice turnbacks are good training but its in the context of a canned scenario, with everything going according to plan and with forewarning. A real engine failure will never be like that. Having said that practicing a turnback once every six months in the aircraft is, in my opinion, setting yourself up for a scare or worse so I'm strongly of the mind that practice turnbacks belong in the simulator only. If you must practice turnbacks in the aircraft then it must be properly supervised and documented. Even then the scope for someone to go off script is precipitously high.
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Old 19th May 2017, 03:55   #23 (permalink)
 
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If the PT6 doesn't feather no one you'll have plenty of sink rate!
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Old 19th May 2017, 04:22   #24 (permalink)
 
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Feathered v unfeathered in the PC9 is a RoD difference of close to 2000 fpm. With a feathered prop you'll get a RoD of 2000fpm, unfeathered is close to 4000fpm.

The prop failed to feather on a PC9 in flight shutdown in 2011, leaving two pilots swinging under parachutes. The aircraft crashed about 1-2nm short of making it back to the airfield.
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Old 19th May 2017, 05:36   #25 (permalink)
 
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Do the Central Section and Western Ops have a simulator these days for training/ practice turn backs and the cloud break proceedure?

King Air pilot training has moved on from assymetrics in the aircraft to comprehensive simulator training. Just wondering, has PC12 pilot training made a similar step forward?
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Old 19th May 2017, 08:45   #26 (permalink)
 
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No Sim. All training is done in the aircraft. It is a real eyeopener when you see it done the first time.
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Old 19th May 2017, 08:53   #27 (permalink)
 
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I've done it probably 20 times in my aircraft and can get away with 280 ft, with a 90 degree crosswind up to about 5 knots. Once those wind figures change, it all goes pear-shaped.

Certainly not for the beginner and certainly not for the experienced when operating beyond known and tested figures. If I added a passenger I'd have to add close to 100ft. If you are going to do it, it would need to be a sizeable margin to be sure you could do it every time, be at the top of your flying game, be well practiced and be alsolutety ready to action on a shutdown.
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Old 19th May 2017, 09:09   #28 (permalink)
 
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Quote:
Originally Posted by Slezy9 View Post
Feathered v unfeathered in the PC9 is a RoD difference of close to 2000 fpm. With a feathered prop you'll get a RoD of 2000fpm, unfeathered is close to 4000fpm.

The prop failed to feather on a PC9 in flight shutdown in 2011, leaving two pilots swinging under parachutes. The aircraft crashed about 1-2nm short of making it back to the airfield.
Do you think the pilots leaving might have had some effect on best glide performance? The fact that an aircraft without pilot or canopy crashed short of the runway is no proof that it wouldn't have made it otherwise.
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Old 19th May 2017, 11:05   #29 (permalink)
 
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Originally Posted by Squawk7700 View Post
I've done it probably 20 times in my aircraft and can get away with 280 ft, with a 90 degree crosswind up to about 5 knots. Once those wind figures change, it all goes pear-shaped.

Certainly not for the beginner and certainly not for the experienced when operating beyond known and tested figures. If I added a passenger I'd have to add close to 100ft. If you are going to do it, it would need to be a sizeable margin to be sure you could do it every time, be at the top of your flying game, be well practiced and be alsolutety ready to action on a shutdown.
Do you have an airspeed and height gate or just a height?
What rule of thumb for temperature and density altitude do you use?
What analysis of the 'power loss' do you allow for before deciding to shut down the engine?
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Old 19th May 2017, 11:11   #30 (permalink)
 
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Quote:
Originally Posted by Chronic Snoozer View Post
Do you have an airspeed and height gate or just a height?
What rule of thumb for temperature and density altitude do you use?
What analysis of the 'power loss' do you allow for before deciding to shut down the engine?
That's the issue... power loss... what constitutes power loss. Do you shut down at the slightest splutter? DA, who knows, that's at sea level 1013. Too many variables even on a simple light aircraft let alone something big to be safe.

Add a massive margin and of course you'll get back, but at that point it's hardly a turn-back on takeoff.
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Old 19th May 2017, 12:08   #31 (permalink)
 
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Quote:
Originally Posted by Cloudee View Post
Do you think the pilots leaving might have had some effect on best glide performance? The fact that an aircraft without pilot or canopy crashed short of the runway is no proof that it wouldn't have made it otherwise.
In the end the lack of a canopy made no difference. The pilots departed the scene below 300 feet (below MEDH). Unfortunately the full accident report doesn't seem to be available online.
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Old 19th May 2017, 14:11   #32 (permalink)
 
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That's the issue... power loss... what constitutes power loss. Do you shut down at the slightest splutter?
That is a very good question. In the Sheppey Post No 19, he mentions the Winjeel fatality (which happened at Point Cook). Shortly after take off when about 700 feet, the instructor announced to ATC "Simulated engine failure". However the student failed to immediately lower the nose although the aircraft was observed to start a steep turn. Passing through 90 degrees the Winjeel stalled and flicked into an incipient spin.
The instructor presumably took action to recover from the incipient spin as he had the wings levelled shortly before impact but the aircraft hit the airfield at a high rate of descent. The landing gear collapsed, the battery broke free at impact causing arcing and ignited fuel from the fuel tank adjacent to the battery. The aircraft caught fire and the two pilots were unable to open the canopy to get out before being overcome by the flames in the cockpit.
Fire crews were on the scene within two minutes but due to the haste to get foam going, the driver inadvertently selected wrong selections and there was no foam. A fireman who tried to force open the Winjeel canopy was driven back by flames.
While the simulated engine failure by throttle closure started the chain of events in this case, a ditching into the sea straight ahead (simulated) would have been the safer option rather than a turn back with its associated risks of mis-handling at low altitude.

Quote:
There are strict gates that must be met and a turn back is limited to the QFIs.
This would suggest that even experienced RAAF pilots who are QFI's appreciate that a high degree of flying skill is a vital factor in the conduct of a successful turn back manoeuvre; otherwise why not allow students to practice these solo? In the case of the Winjeel accident, the instructor was certainly experienced yet a vital few seconds slow to react to the student not lowering the nose prior to turning back.

Quote:
Having said that practicing a turnback once every six months in the aircraft is, in my opinion, setting yourself up for a scare or worse so I'm strongly of the mind that practice turnbacks belong in the simulator only
Isn't that why CASA mandated emergency manoeuvres for certain aircraft types must only be done in a simulator?

Last edited by A37575; 19th May 2017 at 14:37.
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Old 20th May 2017, 00:25   #33 (permalink)
 
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This comment from a former RAAF CFI of CFS in the era when turn backs in Vampires were first introduced at East Sale where there were two runways

Quote: "It's a bit like airline pre take-off briefs as you and I would have done them.

The brief would be specific for the take off.

When discussing turn backs they are thinking of back to the same runway . but as I mentioned before ...off on 27 at East Sale a turn to land on runway 02 (I think) would be possible PROVIDING the aircraft had enough ENERGY...i.e. height and speed and distance from the field.

So all the talk about great gliding and stuff is only applicable when the 3 issues I mentioned are satisfied ...otherwise in the case of the military PC aircraft it would a be a zoom and boom eject I expect.

IT IS ALL predicated on the three items above and a specific brief for the specific take-off runway ...think about the brief for EFATO at Kagoshima in Japan.

If they want to be hero's today and dead men tomorrow let them be. Practise it enough and statistically the result will be predictable." Unquote.
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Old 20th May 2017, 00:47   #34 (permalink)
 
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From ADF Serials, and sounds like the accident to which sheppey refers.
Quote:
CA25-33, Crashed 06/61, Point Cook.
It was being flown by an Army cadet and an RAAF instructor. Apparently the engine failed soon after take-off and the pilots attempted to regain the airfield. However the aircraft stalled and crashed on the airfield. Sadly, the engine broke away, passing under the fuselage and rupturing the fuselage fuel tank which quickly caught fire and probably caused the deaths of the crew. New trainees were shown the gouges in the ground where the aircraft struck to remind us to try to land straight ahead in the event of engine failure on take-off and never to try to turn back to the airfield.
The last sentence tells me that it was what the crew did, not that it was a procedure endorsed by the RAAF, and on which crews were trained for on that particular type.
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Old 20th May 2017, 01:23   #35 (permalink)
 
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Quote:
The last sentence tells me that it was what the crew did, not that it was a procedure endorsed by the RAAF, and on which crews were trained for on that particular type
I can offer some light re turn backs on Winjeels. I was a QFI at Uranquinty in 1956 on Winjeels when the type was first introduced. Certainly turn backs were never considered as a training exercise.
Several years later circa 1960 we had a Winjeel at No 10 Squadron Townsville along with the Lincoln Mk 31 Long nose. By then I was the squadron QFI on the Lincolns, Winjeel and the unit Dakota.

A new Squadron Leader arrived on posting to Townsville to be flight commander. He came from CFS where he was an instructor. There were Winjeels at CFS and he was experienced on type.

As was customary, it fell to me to give him a dual check on each aircraft he would fly at Townsville, including the Winjeel. We took off from the then Runway 02. It is a long runway. At around 200 feet I closed the throttle and announced "simulated engine failure" full expecting he would lower the nose and land straight ahead on the ample length remaining. I planned to tell him to go-around once it was clear he could easily land ahead.

Instead he simultaneously lowered the nose and ripped into a 60 angle of bank through 180 degrees turn to land back the way we came. I was unable to prevent this happening as any interference in the turn would be potentially dangerous. The aircraft touched down nicely and we stopped. ATC were not expecting this and nor was I.

After a short and serious discussion about this antic he explained that CFS taught turn backs in Winjeels. I had never heard of this before.
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Old 20th May 2017, 19:23   #36 (permalink)
 
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I think it's excellent that someone has had the balls to consider that a turn-back is a sensible manoeuvre for a high performance aircraft. The moment you achieve a climb rate in excess of your glide angle this procedure becomes sensible. All you have to to is ensure you have enough sky underneath you to do a 180. The rest is in training. Not to do so risks wasting a valuable airframe. It's about time thinking was introduced to aviation.

PM
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Old 20th May 2017, 19:31   #37 (permalink)
 
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We practice this in the PC12 (usually in OPC), never below 1000ft AGL and in VMC of course. In sim I have tried it little lower. It certainly is doable, however many a pilot has stalled and spinned performing that turn..
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Old 21st May 2017, 00:49   #38 (permalink)
 
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Coincidentally (or scarily) a suggested post popped up in my Facebook feed from Martin Baker today. It has some pictures and a first hand account of th PC9 crash in East Sale.

Quote:
I lurched slightly forward in my seat as I felt the engine suddenly wind back and heard the cockpit go eerily quiet. I quickly scanned the engine instruments and systems display to see a decaying engine and a concerning amount of red coloured warning captions.
Not entirely ready to accept that this was an unrecoverable flame out, I started carrying out the immediate actions for an engine failure/loss of power. The first step was to convert excess speed to height, turn to point the aircraft towards the nearest suitable field and capture the best glide speed.
At first glance the ‘visual picture’ out the front indicated we were going to make our departure field safely. Not long after that the front-seat instructor took over and we continued the checklist actions in an attempt to relight the engine, but to no avail. Getting very low on altitude, it was apparent that the glide was no longer performing as expected and we weren’t going to make the runway.

...the high-pressure fuel pump which starved the engine of fuel and resulted in a flame out. An unfortunate second malfunction caused the propeller to fail to feather correctly which drastically reduced the expected glide potential."
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Old 21st May 2017, 01:39   #39 (permalink)
 
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CS, from a student about to graduate at Pearce.
Quote:
No turn backs are taught to the students. Instructors can do it. We can only got to the duty runway, the lane, or if conditions are favourable the cross runway and our turn back for that was 1500 agl
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Old 21st May 2017, 01:57   #40 (permalink)
 
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Quote:
At first glance the ‘visual picture’ out the front indicated we were going to make our departure field safely. Not long after that the front-seat instructor took over and we continued the checklist actions in an attempt to relight the engine, but to no avail. Getting very low on altitude, it was apparent that the glide was no longer performing as expected and we weren’t going to make the runway
I sweated that out even reading it
The rate of descent with a windmilling prop in a turbo-prop is startling. During my conversion to the RAAF Viscount (four Rolls Royce Dart turbo-prop engines) many years ago, we were doing circuits on Runway 35 at Canberra. While downwind on one circuit, the instructor told me to try a glide approach. That meant maintaining circuit height on base leg until it was judged that if we closed the throttles to idle we should be able to get in from there. In retrospect the whole exercise was potentially dangerous and we should never have even contemplated it. But the instructor had been shown this when overseas being checked out on his own conversion to the Viscount

I held height until I was absolutely certain we could glide safely from throttle closure then smoothly brought all four Darts to idle. The speed drop off was alarming and we had to lower the nose a lot. The rate of descent soon became drastic and it became obvious we were going to land a mile short of the threshold. My guess was the glide angle at idle was around 10 degrees.

Naturally that wasn't on, so power was quickly re-introduced to approach power to get back to hold the normal three degree slope.
The lesson learned was never to under-estimate the glide angle with a windmilling turbo-prop.

Last edited by Centaurus; 21st May 2017 at 06:40.
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