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I saw an Alouette III starting and only after some minutes the rotor started moving...
The astazou is a fixed shaft engine, right?
I would like to hear from a pilot how the system works for the start, rotor brake? manual clutch?
Any links about fixed shaft turbines in helicopters would be apreciated.
Regards
Aser
Lama Bear
26th Oct 2005, 22:34
If it was an Alouette III it probably had an Artouste IIIB engine, the big brother of the Astazou. It is a fixed shaft engine with a centrifugal clutch mounted on the drive shaft connecting the engine and transmission. There are two different clutches, the standard and the unified. The major difference to the pilot was the engagement rpm.
The clutch system worked well IF the pilot used proper technique. Both clutches had a 10 second window for proper engagement. Faster than 35 seconds and you were using too much of the clutch shortening it's life. Longer than 45 seconds glazed the clutch.
The clutch is a frequent source of high frequency vibrations.
Great helicopters and great engines if you don't mind the high fuel consumption and noise.
bendix
27th Oct 2005, 11:25
The Chief Test Pilot of SUD AVIATION once said:
" The Artouste III B will never fail as long as is gets fuel":cool:
bendix
Lama Bear
27th Oct 2005, 13:38
When I first started flying Lamas all Artouste engines were sent back to France for overhaul. At that time (1975) the school said that there had never been an in-flight failure of an Artouste. Unfortunately demand became so high that others were given overhaul privileges. Since then there have been failures. It is truly one of the great engines. It's too bad the start system was so complex and touchy.
I was looking for more info when I read:
Its prototype (model SE-3120) holds the world record for the longest ever sustained helicopter flight, of 13 hours and 56 minutes. These helicopters have a lot of history!
The helicopter's power plant is a 790 shaft horsepower, Turbomecha Artouste 2 - series C-6 engine with 473HP governor. This model engine also has an impressive history all its own. In the history of aviation, no C-6 has ever failed in flight on any aircraft in its production and service history!
from http://www.tigercopter.com/history/alouette.html
Also
ALOUETTE II (AEROSPATIALE)
Alouette 2 was the first turbine-powered helicopter in the world to go into production.
Interesting...
Lama Bear:
I dont' understand.. "It is a fixed shaft engine with a centrifugal clutch mounted on the drive shaft connecting the engine and transmission. " So when you start the engine the rotor starts moving or not?
"The major difference to the pilot was the engagement rpm.
The clutch system worked well IF the pilot used proper technique. Both clutches had a 10 second window for proper engagement. Faster than 35 seconds and you were using too much of the clutch shortening it's life. Longer than 45 seconds glazed the clutch."
:confused:
centrifugal, manual or what?
What's the rpm for rotor engagement?
I'm sorry but I'm lost.
Thanks anyway
;)
Lama Bear
27th Oct 2005, 16:51
I'm sorry I didn't really answer your question completely. My error :-(
"I don't understand.. "It is a fixed shaft engine with a centrifugal clutch mounted on the drive shaft connecting the engine and transmission. " So when you start the engine the rotor starts moving or not?"
The rotor system does not start moving with the engine starting. The rotor system is isolated by the clutch. The rotor brake may or may not be applied during the start. I usually did not have the brake on unless there was a high wind condition or there was creep because the clutch was dragging. A dragging clutch was not common and was a condition for removal if the idle rpm was set properly. The reason for all this was to insure that a rotor blade was not parked over the engine exhaust resulting in damaged blade. Allouette and Lama pilots always stop the rotor system with a blade in front. For me it carries over into the Astar. By the way the rotor brake system was excellent. The French make great rotor brakes.
"The major difference to the pilot was the engagement rpm.
The clutch system worked well IF the pilot used proper technique. Both clutches had a 10 second window for proper engagement. Faster than 35 seconds and you were using too much of the clutch shortening it's life. Longer than 45 seconds glazed the clutch."
centrifugal, manual or what?
The clutch is centrifugal, controlled by engine RPM. As the engine RPM comes up mechanical fly weights inside the clutch make contact with the inside rim of the clutch, very similar to Bell 47 system. The pilot controls the engagement in the manner that he/she increases the fuel flow to the engine from idle. As the fuel is increased and the blades start to move a stop clock on the panel was pushed. This started the 35-45 second window for engagement. There was also a maximum T4 (EGT, TOT) increase during an engagement. If this was exceeded it was an indication that you had a severely worn clutch and it needed new shoes.
What's the rpm for rotor engagement?
I'm sorry but the exact numbers have faded with time. I am in Mexico and my books are in the US. I would be happy to get some real numbers to you as I go on break next week. Don't quote me but I THINK the Standard clutch was 17,000 to 19,000 rpm and the Unified was 19,000 to 23,000. And remember the whole engine is turning at these rpm's. The unified clutch was also used on the Gazelle. It was interesting to become accustomed to the Standard clutch and then get in a ship with the Unified, seemed like it was never going to start turning.
These are grand old ships. If you ever get a chance to fly one don't turn it down. I will say they are probably harder to get comfortable with than any other I have transistioned into. It usually took pilots several hundren hours to get used to all their noises and vibrations, let alone be able to work one anywhere near thier maximum capability.
I'm sorry but I'm lost.
Thanks anyway
And you have me for a guide???? You are truely lost! :-[
Thanks!
The clutch is centrifugal, controlled by engine RPM. As the engine RPM comes up mechanical fly weights inside the clutch make contact with the inside rim of the clutch, very similar to Bell 47 system. The pilot controls the engagement in the manner that he/she increases the fuel flow to the engine from idle.
That is what I was looking for.:ok:
Don't worry about the numbers I understand that the rpm is so high for engagement that you can stay at idle without the rotor turning.weird system but interesting.
Best regards
Aser
These principles remain the same with the Astazou which is fitted to the Gazelle. Ground idle RPM is 25,500 +/- 400 and the centrifugal clutch engages as the RPM is increased to 43,700 +/- 400 at flight idle.
HEDP
Oh yes they were great helicopters very forgiving who seemed to share a complicity with their more or less skilled skippers....It is true that it seems that failures on Artouste / Aztazou engines, that never happened before occurs now. One of the causes could also be the gap between "old" and "new" engineers generation...
This put apart, and to come back to clutches, on the first Alouette 2 (SE 3130) if I remember well,there was oil inside the clutch instead of weights, there was then no time limitation, just an indication stating that synchronisation should be completed within 50 sec. The rotor was then starting to turn on start-up.
Latter models of clutches were fitted with weights and some oil, with a time slot to synchronise (but also with rotor winding up on start up)
Thanks again to designers of this time !
bendix
28th Oct 2005, 07:02
The Alouettes II and III' are great machines
The clutch system has the advantage that you can close the fuel flow to idle 16,000 rpm ,stop the rotors,taking care to stop one blade in front and keep it there while you do a hot refuel or load
a patient.:cool:
bendix
...... problems started with this engine when the TBO increased progressively from 800 H to 2400 H.
Cheers
ATN