Aurigny Trilander Aircraft

[depolox4]

I have occasion to fly to Alderney now and again, and as always in a Trilander. This last trip I was sitting in the row just behind the pilot, and at the top of the climb I noticed he adjusted the throttle then adjusted the RPM levers (to synchronise the RPM of each engine maybe?), my question is: How can the RPM change without the throttles being altered. Does the RPM lever alter the pitch of the propellers thus taking more or less "bite" of the air, or are the throttle and RPM controls interconnected.

Thanks

[Richard Le page]

I think its the propeller condition lever that alter the pitch of the propeller which makes it sound like the RPM is changing.Its very noticable on air craft like the Dash8 and ATR,especially the older models,I think on newer models[Q400 and ATR-500 its computer controlled and the change in pitch sound is less prominent.]

I think its hard for the pilot to synchonise the RPM of each engine on the trislander so they are in harmony with each other cause when I have travelled in a trislander the engines seem to be all over the place.

maybe someone can give a more technical explanation

Regards.

[depolox4]

Thanks for that, but there separate levers defintely marked RPM and Throttle. The throtlle levers were not all in same place but that is no doubt due to loss of motion in the linkages, but the pilot adjusted the throttles to a position, adjusted the mixture controls, then took a lot of tweaking of the RPM controls.
Yes I agree on the Dash 8 the change of propeller pitch is very noticable on landing, and taxi.

[Richard Le page]

The trislander is very much a hands on aircraft and the engines go out of sync very easily,They need constant tweaking by the pilot to keep them relatively in sync with each other.

[depolox4]

Thanks for the reply again, maybe I wasn't clear enough with my question. Once the speed of the engines have been set by the throttles, (black levers)...i.e say 2750RPM, and the throttle lever settings are not altered, how does adjusting the RPM control (blue levers) alter the engine speed. The only way I can see this happening is by altering the pitch of the propeller, therefore adding or removing load from that particular engine.

Cheers
Depolox

[White Knight]

think its the propeller condition lever that alter the pitch of the propeller which makes it sound like the RPM is changing.Its very noticable on air craft like the Dash8 and ATR,especially the older models,I think on newer models[Q400 and ATR-500 its computer controlled and the change in pitch sound is less prominent.]


Big difference here. The Trislander is PISTON ENGINED and the Dash8 and ATRs are TURBINE

On the Trislander the throttles controls Manifold Pressure - in other words the raw power in the engine, and the prop levers control the RPM. The engine can take (and provide) more of the raw power when the props are spinning faster. However, in different phases of flight you need different power settings. So, after takeoff the pilot will reduce the manifold pressure with the throttles and then reduce the RPM. Less power = less fuel = less noise (which is quite something with the Trislander).
On, say the ATR, the condition levers control the fuel flow to the engine for starting and shutdown (via a small lever at the base of the main lever) and RPM, and the throttles control the torque - again, the raw power.

As for the Trislander and the many myriad adjustments made by the pilot? Well, simply to keep the props in synch and try and reduce the noise in the cabin. Each aircraft (and I'm talking the Aurigny fleet of Tris that I flew for two years) had different positions for the prop levers for a certain RPM. The levers would be staggered differently for each 'plane. We would learn the sort of positions required - and then the engineers would re-rig during the normal checks and we'd have to re-learn the required prop synchs!!

Depolox4 - you are correct in that the prop levers alter the RPM and give a different bite of air. As I said the throttle controls raw power as an accelerator does in a car. They are NOT physically interconnected on the Trislander, although the pilots have standard settings such as 25" Manifold Pressure and 2500 RPM for the climb.

Hope this helps. I like talking about the Tri having flown it for so many years:ok::ok::ok:

[Avionker]

I guess after many years of flying those things it's best to write the question down for you though?

CAN YOU HEAR ME WHITE KINIGHT? HELLO? :)

[depolox4]

Many thanks White Knight explains it all now, so by that I take it there isn't any pitch adjustment of the propellors.

With you there Avoniker, on my first flight in a Tri didn't realise earplugs might be needed, Never made that mistake again.

Cheers

depolox

[White Knight]

Depolox - there IS pitch adjustment of the props. That's what the prop lever controls. The pilot sets the RPM and the 'Constant Speed Governor' will vary the pitch to maintain the RPM set by the pilot for that phase of flight. Basically the Governor uses oil pressure and flyweights to control the pitch of the propellor.

Google Constant Speed Governor for a detailed description.

Cheers:ok:
WK

[depolox4]

Thanks WK,
Very informative, just as another matter of interest, do the Tri engines have carburettors or are they fuel injection.

Always thought the flights in Tri's far more interesting than say ATR or Dash8's being that I travel to all of Channel Islands quite frequently.

Cheers


Depolox

[srobarts]

Looks like carburettor to me:
Lycoming O-540 - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Lycoming_O-540#Specifications_.28IO-540-K1A5.29)

[White Knight]

Carbs all around..... The carb heaters are low on the throttle quadrant and you'll see the pilot bending down to reach them. Very effective too - these engines run very well in all kinds of heavy carb-icing weather:ok:

[radiosutch]

Youtube has plenty of videos of what is mentioned above

YouTube - G-JOEY 1 Jan 2005 Aurigny to Jersey is just one.

[xtypeman]

Ah JOEY pride of place on my study wall is my JOEY certificate..........

Oh and just a touch pedantic Trislander.