Go Back  PPRuNe Forums > Aircrew Forums > Rotorheads
Reload this Page >

Alvis Leonides

Rotorheads A haven for helicopter professionals to discuss the things that affect them

Alvis Leonides

Old 20th Jan 2019, 17:11
  #1 (permalink)  
Thread Starter
Join Date: Aug 2006
Location: Oop North
Posts: 108
Alvis Leonides

A pal of mine is currently restoring an Alvis Leonides from a Westland Whirlwind. He'd appreciate anyone who could direct him to a source of spares. Pse PM.
Marly Lite is offline  
Old 21st Jan 2019, 07:08
  #2 (permalink)  
Join Date: Nov 2001
Location: Norfolk
Age: 80
Posts: 291
Must be a Leonids Major if it is from a Whirlwind.
rotorfossil is offline  
Old 25th Jan 2019, 10:11
  #3 (permalink)  
Join Date: Apr 2017
Location: England
Posts: 44
I have a spare hammer he could use for smacking the cartridge starter when it jams - as it surely will.............................
Georg1na is offline  
Old 25th Jan 2019, 10:29
  #4 (permalink)  
Join Date: Jun 2002
Location: east ESSEX
Posts: 3,367
Not sure if a 5d piece will work as a safety disc either.....
sycamore is offline  
Old 25th Jan 2019, 10:45
  #5 (permalink)  
Join Date: Sep 2009
Location: Just over the road from Bicester airfield
Age: 76
Posts: 360
Ah Sycamore , from days past eh ?, all those little fix its that got and kept those flying machines going.
zetec2 is offline  
Old 25th Jan 2019, 11:08
  #6 (permalink)  
Join Date: Mar 2018
Location: Central UK
Posts: 291
Musta been a long long time ago -I know we're talking Whirlies but has a 5d piece been seen since Plantaganet times?
meleagertoo is offline  
Old 25th Jan 2019, 12:38
  #7 (permalink)  
Join Date: Apr 2017
Location: England
Posts: 44
Originally Posted by meleagertoo View Post
Musta been a long long time ago -I know we're talking Whirlies but has a 5d piece been seen since Plantaganet times?

We used silver thruppenny bits being rather upmarket.....................!
Georg1na is offline  
Old 25th Jan 2019, 13:36
  #8 (permalink)  
Join Date: Oct 2006
Location: UK
Posts: 4,627
I have a spare hammer he could use for smacking the cartridge starter when it jams - as it surely will.............................
No need for a hammer with a Sycamore engine; it had an electric starter.

I posted this a few years ago.

I had been to Tern Hill before doing my basic training with the Provost T1. The Bristol Sycamore, our basic helicopter trainer, had the same type of engine, the Alvis Leonides. Between the Valiants folding and my rotary wing course I had got a few hours in the Chipmunk so I was reasonably au fait with suck, squeeze, bang and blow; one at a time.

The cockpit instruments were conventional suction driven with the addition of your staff of life, the dual taco Engine and Rotor rpm. Just to make things difficult the boost gauge had been changed from LBS to Manifold Air Pressure so +8 boost was now something like 46 ins. There was no hydraulic assistance so the controls were low geared and heavy. To alleviate this there spring tensioned pitch and roll trim wheels arranged conventionally to assist the cyclic. This was high tech compared with early S51s that had loops of bungee strategically placed around the cockpit so that the cyclic could be restrained by a convenient loop. A follow on from the restricted control range was a matter of fuel and passengers. These were all in front of the rotor mast so to keep the CofG correct there was a tank of glycol/water mix under the cockpit floor. This was controlled by a two-way switch that pumped it back or forwards to a tank at the end of the tail boom to adjust the CofG. Get this wrong and you were going backwards or forwards fairly rapidly when you got airborne. The S51 had a weight that the pilot slid along the floor. The problem with this was that he was always moving it uphill. (Think about it)

28th June 1965, I stepped into the Right Hand Seat (normal with helicopters) of XJ384 for my first attempt. The introduction to the cockpit followed observing that there were dual controls but only one collective so relaxing ones hand so the instructor could recover us from disaster was paramount. The dual tacho gauge looked like a torture chamber. I was used to 2,800 rpm +4 of boost being take off with 3,000 +8 for emergency. Judging by the bands on the Rotor Taco the engine was in this range all of the time.

Starting was electric. The left hand operated the co-located starter and booster pump switches, the right hand held the throttle and the knees held the cyclic in case the rotor started moving. This was because there was a centrifugal clutch between the engine and gearbox which started engaging at about 1,000 engine RPM. The plan was to start and idle at 800 RPM without engaging the clutch but depending on the engine this could not be guaranteed. We started, warmed it up and my instructor lifted into the hover. I was right; the engine was roaring away at full bore with everything shaking and rattling. We then hover-taxied to a quiet part of the airfield for ‘Effects of Controls’. I was showed how to work them one plane at a time and it did what it was supposed to do and then I was given it to hover.

It sat there, five feet above the ground, motionless and as solid as a rock. This is easy, I thought; where were all the horror stories I had heard about helicopters, this is a piece of cake. Just then a faintest whisper of a draught, not even a minor zephyr, wafted onto the port side. The aircraft, in perfect balance, drifted to the right. I corrected and it banked slightly to the left. This changed the lift equilibrium so it sank which I corrected by lifting the lever which increased the drag on the disc which caused it to reduce Rrpm. I caught this by opening the throttle which increased the torque so the aircraft turned to the left so I inputted right rudder which increased the loading so the Rpms dropped again. Meanwhile the aircraft was drifting off to the left and climbing. I corrected by lowering the lever which caused the aircraft to turn right which changed the wind direction to the rear quarter so the aircraft drifted forward and sideways. I pulled the nose up to stop it with the result that the tail rotor’s thrust line went below the main rotor hub so the aircraft rolled to the left. I put in too much forward and right input so the aircraft pitched violently forward and right and started a rapid descent. I pulled up more lever, the rpm dropped so I opened the throttle and this caused the aircraft to turn left so the wind got behind and pushed the tail up again and as I was trying to level it the wind pushed the tail around so I was facing a different way which I tried to correct with tail rotor which made the rpm go up again so I closed the throttle and it turned and sank and drifted rapidly to the left.


“I have control”, and I felt the instructors hand take over the collective and the world stabilised and came back into focus.

We went through the effects again and the next time was slightly better but then it was time to leave the circuit. I followed lightly on the controls as we increased forward speed. At about 30 knots there was a violent shudder and roll from the aircraft which almost immediately disappeared. This was the transitional buffet. What happens is that there is one set of rules in the hover and another one in forward flight and the transition is where a new pack of cards is shuffled. Once it’s past that then it follows almost fixed wing characteristics.

In the cruise at 100 knots it was almost normal. The trim wheels worked fine and one could let it fly itself for a short time and the rotor rpm was fairly stable. After a time there was not a lot of difference from having a Leonides blaring away in front of you to one blaring away behind.

We returned to the circuit and after a standard pattern we approached to land. I was reminded at about 100 feet to put the trim wheels at 2 degrees right and 2 degrees back as that would put the controls to where you wanted them when you got into the hover. Not too many disasters and now my first flight was over so we staggered over to the dispersal to shut down.

Once on the ground the throttles were retarded so that the engine ran at 1,200 rpm to cool down. Then the throttle was closed to idle. This is when one looked into the mirror at the top of the windscreen to check that the droop stops were in.

Droop Stops are wedge shaped things that restrict the downwards flapping of the blades at low Rrpm so that they don’t chop the tail off. They can be seen on the rotor head picture extending out of the top of the picture. They each have a weighted ball on the end which will fly out at high rpm and withdraw the wedges against a spring. Conversely the spring will force them and the wedges back when the rotor slows down. Should one fail and this can be seen by one of the balls not rotating the same as the others then there is a high risk of a blade hitting the boom.

In that case we go to Plan A:

The rotor is accelerated and decelerated a few times with small movements of the cyclic to try and centralise them.

Should that not work we go to Plan B:

A fire engine comes along and positions a large hosepipe to the right rear of the rotor disc. The blades rotate clockwise looking from above so it is on the side before they reach the boom. A jet of water is then directed just over the boom in front of the tail rotor and the engine is shut down. As the rotor decays and the errant blade sinks it lands on top of the water jet and is carried over the boom. The blades, although wooden, were made by real carpenters so they were unaffected by this sudden dowsing.

Should there not be a fire engine available then we go to Plan C:

There isn’t a Plan C.

What they had to do was to place a large think blanket over the boom at the critical point where the blade would hit it. The mass balances on the blade tips looked like 20mm cannon shells and as such they would bounce off this as they went around. In practice there were only two of three thumps and then the blades stopped. No blanket: Bang, Bang, Thud, unless you were very lucky.

This time there was nothing untoward and that was it for the day and being Friday it was off for the weekend.
Fareastdriver is offline  
Old 25th Jan 2019, 13:45
  #9 (permalink)  
Join Date: Sep 2006
Location: Inside the Industry
Posts: 752
Always enjoy reading your accounts, FED, you write just how you used to tell the stories to us “young blokes” as we were then! Thank you.
industry insider is offline  
Old 25th Jan 2019, 20:29
  #10 (permalink)  
Join Date: Dec 2001
Location: Gold Coast, Queensland
Posts: 917
In Borneo we used a Malayan 10 cent coin when the starter safety disc blew. Before starting the engine we had to turn the crank handle 72 times for 1 engine revolution to make sure the lower cylinders didn't have oil leaked into them over night! We also cranked started in the bush if we ran out of starter cartridges, you had to crank really fast & with luck, 1 cylinder would fire, then another & finally all of them! Only ever had the inlet manifold crack, so quite reliable, it was the clutch that caused most problems I think!
Nigel Osborn is offline  
Old 25th Jan 2019, 20:55
  #11 (permalink)  
Join Date: Jun 2002
Location: east ESSEX
Posts: 3,367
Nigel, surprised that with matelot`s `make do and mend` attitude,nobody made an `APU` out of a Honda50 moped and a `Hucks `starter attachment engaged,life would have been easier...
alternatively,engage clutch,fit tip -socks,and dance around the `maypole`....!
Anyway the WW Mk3 was easier,with a Cyclone and electric starter...
sycamore is offline  
Old 25th Jan 2019, 21:22
  #12 (permalink)  
Join Date: Jan 2000
Location: Bar to Bar
Posts: 711
Sycamore, I am two if not three generations beyond that but couldn't believe my fortune when the Red Bull landed on our pad at Filton......opposed by the Concorde Hangar where it was supposed to be. Positioning flight with a guide was called for, thank you Blackie, one of the most privileged flying days of my life. No hydraulics. One collective. Nr so low by design you can see the individual blades. Over controlling. Schoolboy grin at the wrong side of mid-fifties, priceless.
Sloppy Link is offline  
Old 25th Jan 2019, 21:52
  #13 (permalink)  
Join Date: Oct 2006
Location: UK
Posts: 4,627
The reason you could see the blades was because they skimmed just above the cabin roof. Around 1971 Digger Barrell invited me to Northolt for a drive in one of 32 Sqn's examples. It was only six years since I had last flown it so it wasn't any trouble but I had a 3R duck as the blades passed over the cabin roof.

The last time I ran a Leonides was in the Provost T1 that was used as a taxiing instructor at the Maintenance Unit in Aldergrove. It had an instructional number but the underside of the wings told me it was WV494 which I had flown at Tern Hill. The MU was closing down and the Provost was up for disposal. As far as I could see it was fully serviceable apart from the hood seal and the clock.

The run was in the middle of all their airframes outside their hanger and we were pointing directly at a Pembroke . The run was super, it passed all the tests and it was gratifying to see the blue flame when we had it up to 3,000 and +8 boost. A thought occurred to me that when I had last done this at Tern Hill we had chained chocks and two airmen slumped across the tailplane to stop it nosing over: Not this Time !

I believe it is now in Muscat labelled XF 868.

Last edited by Fareastdriver; 25th Jan 2019 at 22:09.
Fareastdriver is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.