Gazelle: Flying, operating, buying
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Gazelle Movie clips
Hi - Found some great Gazelle Movie clips here for downloading:
http://www.rotorleasing.com/Movies.htm
awsome sound
http://www.rotorleasing.com/Movies.htm
awsome sound
Last edited by nushooz; 26th Sep 2002 at 09:45.
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Gazelle Engine Failure
I recently heard that it is, as yet, unknown for the gazelle (model as operated by the AAC) to have an engine failure. Can anyone confirm or deny this, and if it is true, considering its extensive use in the AAC and RNavy, is this not relatively impressive???
Can somebody in the know please confirm for me that the Gazzelle has a single shaft engine and a clutch?
Any links to cutaway drawings or data would also be helpful?
Cheers
CRAN
Any links to cutaway drawings or data would also be helpful?
Cheers
CRAN
Join Date: Dec 2001
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GAzelle has a single shaft engine (Astazou III) and a clutch, as you surmise.
The reliability of the engine has until now (apparently) been exceptional. Once started, they need something pretty unusual to make them quit - the only failures of this type of engine that I know of involved someone forgetting to put oil in the engine, or forgetting to put the fuel cap on and sucking raw fuel into the intake, or water in the fuel tank (in an Alouette in Romania).
Otherwise, pretty reliable engines. Once you get them started....
The reliability of the engine has until now (apparently) been exceptional. Once started, they need something pretty unusual to make them quit - the only failures of this type of engine that I know of involved someone forgetting to put oil in the engine, or forgetting to put the fuel cap on and sucking raw fuel into the intake, or water in the fuel tank (in an Alouette in Romania).
Otherwise, pretty reliable engines. Once you get them started....
Gazelle Control Restriction
The recent AAIB accident report on G-BZDW (restriction of aft cyclic movement believed to be caused by contact between pilots stick and harness buckle) reminded me of a similar incident in the 70's. Although I believe this could not apply to DW as this aircraft had SAS.
In 1972? an Army Gazelle crashed killing three pax when it failed to recover from a dive. Pilot reported a control restriction in aft cyclic which jammed the stick. No fault was found but the accident was put down to jack stall.
1976/8 (Cant remember the year) XW 851 sister ship to the accident aircraft was on major inspection. While carrying out a control functional check the cyclic jammed solid while travelling aft. The cause was the sliding discs at the bottom of the stick, the lowest had distorted in contact with the floor, the second disc had then jammed into the distortion. The only way to free the stick was to push forward and then pull back again. Not a natural act in a dive!!!!!!
My point is that although the military checked their aircraft as far as I know the civil fleet was never checked and this is very much dormant fault. The first time it happened it took an hour to reproduce the problem.
It is my believe that the cause of the problem was either that the lowest disc diameters either internal or external were incorrect or the diameter of the next disc up was to small. Possibly a combination of the above.
I often wonder if anyone ever told the pilot of the first crash about this or if he has just carried on through the years believing he was possibly at fault.
In 1972? an Army Gazelle crashed killing three pax when it failed to recover from a dive. Pilot reported a control restriction in aft cyclic which jammed the stick. No fault was found but the accident was put down to jack stall.
1976/8 (Cant remember the year) XW 851 sister ship to the accident aircraft was on major inspection. While carrying out a control functional check the cyclic jammed solid while travelling aft. The cause was the sliding discs at the bottom of the stick, the lowest had distorted in contact with the floor, the second disc had then jammed into the distortion. The only way to free the stick was to push forward and then pull back again. Not a natural act in a dive!!!!!!
My point is that although the military checked their aircraft as far as I know the civil fleet was never checked and this is very much dormant fault. The first time it happened it took an hour to reproduce the problem.
It is my believe that the cause of the problem was either that the lowest disc diameters either internal or external were incorrect or the diameter of the next disc up was to small. Possibly a combination of the above.
I often wonder if anyone ever told the pilot of the first crash about this or if he has just carried on through the years believing he was possibly at fault.
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Very interesting point.
The real questions -
a) why did you need full aft stick in the first place. This should never happen in either civil or military use- the certification should show that there is adequate control margin for all conditions of weight, CG, airspeed, etc.
b) what would you do after recovering from the control jam? I don't mean inflight - I mean after the flight is over. This should be reported to the necessary authorities. Most militaries have flight safety systems to report this stuff, but in the civil world, what do you do? Most civil authorities have an SDR (Service Difficulty Reporting) system that tracks mostly maintenance-related difficulties. The authorities use this to track problems and possibly issue Airworthiness Directives based on what is reported. But it has to be reported!
I would suggest that an SDR would be in order - I don't think you need to be a maintenance person to report anything.
The real questions -
a) why did you need full aft stick in the first place. This should never happen in either civil or military use- the certification should show that there is adequate control margin for all conditions of weight, CG, airspeed, etc.
b) what would you do after recovering from the control jam? I don't mean inflight - I mean after the flight is over. This should be reported to the necessary authorities. Most militaries have flight safety systems to report this stuff, but in the civil world, what do you do? Most civil authorities have an SDR (Service Difficulty Reporting) system that tracks mostly maintenance-related difficulties. The authorities use this to track problems and possibly issue Airworthiness Directives based on what is reported. But it has to be reported!
I would suggest that an SDR would be in order - I don't think you need to be a maintenance person to report anything.
I'm not sure that in the case of the recent crash that full aft cyclic was involved. In the 1970's incident the cyclic jammed a long way forward of full aft.
As to the reporting side I think the lack of interface between the military and the civil side has been well documented and I believe that as far as the UK is concerned major improvements to the transfer of information were implemented a number of years ago.
On a personal level, I wrote up this whole saga with some rather artistic drawings a number of years ago which I submitted to
the CAA via GASIL. No one ever got back to me on that one so its probably lining a drawer somewhere.
As to the reporting side I think the lack of interface between the military and the civil side has been well documented and I believe that as far as the UK is concerned major improvements to the transfer of information were implemented a number of years ago.
On a personal level, I wrote up this whole saga with some rather artistic drawings a number of years ago which I submitted to
the CAA via GASIL. No one ever got back to me on that one so its probably lining a drawer somewhere.
I re-read the AAIB bulletin (feb 2003) and as the pilot had sufficient control to attempt a run on it would appear that any jam was again forward of full aft. How the stick could contact the buckle on a five point harness though beats me.
Again I would emphasise that the two incidents are different in that I believe that SAS equiped aircraft do not have the friction discs at the base of the stick. Maybe somebody could confirm that.
Again I would emphasise that the two incidents are different in that I believe that SAS equiped aircraft do not have the friction discs at the base of the stick. Maybe somebody could confirm that.
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Rob_L......Do you know whether dual flight controls were fitted?
If they were, was the front passenger five point harness stowed correctly? I seem to remember something about ensuring the empty seat harness was done up prior to takeoff. If the buckle was left lose and hanging down the front of the seat when dual controls were fitted the rearward cyclic movement could be restricted.
If they were, was the front passenger five point harness stowed correctly? I seem to remember something about ensuring the empty seat harness was done up prior to takeoff. If the buckle was left lose and hanging down the front of the seat when dual controls were fitted the rearward cyclic movement could be restricted.
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Kenny
Quite right, the harness was not stowed correctly and duals were fitted. If the quick release buckle falls forward off the co-pilots seat while the duals are fitted it can restrict the rear movement of the cyclic, the buckle has to fall forward off the seat and come to rest in a precise position to jam the movement but sods law this will happen.
Quite right, the harness was not stowed correctly and duals were fitted. If the quick release buckle falls forward off the co-pilots seat while the duals are fitted it can restrict the rear movement of the cyclic, the buckle has to fall forward off the seat and come to rest in a precise position to jam the movement but sods law this will happen.
The AAIB report says that the contact was with the pilots harness, no mention of duals.
I'm getting my information straight off the AAIB report.
Where is your info comming from Tallguy?
In case anyone is interested on an aircraft with the friction discs at the base of the cyclic you can check for the potential for a control jam by carrying out the following.
Reduce the friction so the discs slide easily.
Have someone hold the stick forward of centre.
Slide the lowest disc as far aft as possible without contacting the floor.
Slide the disc above it as far aft as possible.
Check for a gap between the outer edge of the inner disc and the inner edge of the lower disc.
If there is a gap the potential is there. If the hole in the lowest disc is completely covered, no problem.
I'm getting my information straight off the AAIB report.
Where is your info comming from Tallguy?
In case anyone is interested on an aircraft with the friction discs at the base of the cyclic you can check for the potential for a control jam by carrying out the following.
Reduce the friction so the discs slide easily.
Have someone hold the stick forward of centre.
Slide the lowest disc as far aft as possible without contacting the floor.
Slide the disc above it as far aft as possible.
Check for a gap between the outer edge of the inner disc and the inner edge of the lower disc.
If there is a gap the potential is there. If the hole in the lowest disc is completely covered, no problem.
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Having just had my daily slagging from my friend the helicopter technician, they dont like being refered to as engineers here!!
I would like to add that the Astazou has been totally reliable for 3000 of my flying hours to date. I have flown the Gazelle in various parts of the world in different climates and the engine performed every time. It does have a clutch (dry centrifugal) and a single dual action drive shaft (internal/external) and apart from being French is a sound design.
I would like to add that the Astazou has been totally reliable for 3000 of my flying hours to date. I have flown the Gazelle in various parts of the world in different climates and the engine performed every time. It does have a clutch (dry centrifugal) and a single dual action drive shaft (internal/external) and apart from being French is a sound design.
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Rob_L
I can confirm that Tallguy is correct in that unfastened seat buckles (either side) can and do restrict aft cyclic movement if not fastened, it can quite easily be demonstrated before start up and is such an easy mistake to make with horrible consiquences.
Regards
L N
I can confirm that Tallguy is correct in that unfastened seat buckles (either side) can and do restrict aft cyclic movement if not fastened, it can quite easily be demonstrated before start up and is such an easy mistake to make with horrible consiquences.
Regards
L N
The AAIB report says that contact with the pilots buckle was the suspect cause. I agree that if the harness was open this would cause this type of control restriction.
However I dont know any helicopter pilots who fly unstrapped. More so if they are making an emergency approach for a run on landing.
However if unstrapped with a restriction it might not be possible (mentally) to sort out the problem. I'm still curious as to why the report didnt mention it.
To be honest the accident to ZW wasn' t my interest in starting this thread. I was more interested in the possibility of civil Gazelles flying around with the potential cyclic friction problem.
Still that is the joy of the internet, it does sometimes seem to turn into send three and fourpence were going to a dance.
Sometimes frustrating sometimes fun.
However I dont know any helicopter pilots who fly unstrapped. More so if they are making an emergency approach for a run on landing.
However if unstrapped with a restriction it might not be possible (mentally) to sort out the problem. I'm still curious as to why the report didnt mention it.
To be honest the accident to ZW wasn' t my interest in starting this thread. I was more interested in the possibility of civil Gazelles flying around with the potential cyclic friction problem.
Still that is the joy of the internet, it does sometimes seem to turn into send three and fourpence were going to a dance.
Sometimes frustrating sometimes fun.
Senis Semper Fidelis
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Very interesting thread, we have in our local area two Gazelles, one with the owner pilot who flys it very carefully indeed, but the other local one, the pilot of this, for a party piece to show the unexperienced pax, puts this Gazelle into a near vertical dive and then pulls out at the bottom under full power to land as he says " in style", I have always thought he is pushing it a little but now I am certain he may yet "buy the plot!" sadly though he may have some one sat alongside when that happens
Last edited by Heliport; 6th Apr 2003 at 08:00.
Another cause of cyclic restriction....
Another possible cause of cyclic control restriction in 'civvy' gazelles is the front carpets. The one I fly has the cyclic stuck through a neatly hemmed (with leather piping) circular hole in the carpet. I have known the carpet to shift slightly when climbing in and get partially wedged between the upper and lower cyclic 'discs'. When you do the 'full and free' checks prior to rotor start however, you quickly notice if anythings amiss. I'm very particular about this check on this individual machine to ensure the carpet is correctly seated. J
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Rob
The SAS-fitted Gazelles have the same friction discs on the cyclic as those without SAS. The only difference is that they have been checked 'fully loose' on every startup since they were brought into service, and so are ususally very solidly 'off'!
I have not flown a Gazelle for a long time, but I do seem to recall the occasional interaction between stick and belt-buckle (fastened) during 'full and free' checks. However, the cyclic would not normally need to be brought back to the stops (or the buckle) to pull out of a dive.
The SAS-fitted Gazelles have the same friction discs on the cyclic as those without SAS. The only difference is that they have been checked 'fully loose' on every startup since they were brought into service, and so are ususally very solidly 'off'!
I have not flown a Gazelle for a long time, but I do seem to recall the occasional interaction between stick and belt-buckle (fastened) during 'full and free' checks. However, the cyclic would not normally need to be brought back to the stops (or the buckle) to pull out of a dive.