Hiller UH12E engine - Lycoming VO 540 C2A

 

 

12E Engine operating Tips :

 

RPM and MAP Control.

The big Lycoming VO540C2A engine has plenty of grunt and is de-rated by MAP from 340 to 305 HP by not exceeding 26.0”MAP on a Std day at sea level.

 

Over-boosting tends to cause trouble in the drive train and M/rotor hub. The Bottom Planetary gears wear and the main rotor hub can crack

 

Over-revving (exceeding 3200 Engine RPM) is another matter.

 If you exceed 3520 rpm you can expect a con rod failure (usually Number 5 or 6 ) and sudden engine stoppage  between 150 and 250 hrs after the event.

 

Continuous lesser over-revs will give the same result.

The engine has at least 11 degrees of twist in the crankshaft at rest. This straightens out at operating RPM and power! Use only smooth and slow throttle movements when accelerating up or down in the green Tacho Arc (3200 to 2900 RPM).

 

Read and understand the complete latest version of Lycoming Service Bulletin 369 specifying the maintenance requirements after exceeding 3200 RPM.

 

 

 

Don’t ignore the warnings!! If you think you can fool the engine or hide your error - read the link page "Metal has Memory" on the first page of this website

For long engine life, operate at 3000 – 3100 ERPM, above transition.

 

The yellow arc on the dual Tacho is a system resonance area in which the cooling fan resonates and can develop cracks. Don’t get distracted and stay in that range at any time while idling on the ground – pass smoothly thru up or down.

 

Cold Start (first start of the day) or cold day:

Start engine and stay @1650/1700 RPM (no more) until the cylinder head temp passes thru 50oC. The rattling noises are normal – don’t worry.

When thru 50oC – smoothly throttle up to idle at normal 22/2300.

 

ETIP2: all: carb heat: If at any time in flight you feel that “something is not right” with the engine – your first action, provided that it is safe to do so (height, power requirements etc), would be to pull the carb heat full on. This ensures that any potential carb ice problems are eliminated.

 

 

Piston Helicopter Carburettor – Idle mixture adjustment

 

 

Many normal aspirated helicopter engines have never had the carb idle mixture adjusted since they were run in the test stand at overhaul.

 

Here’s how to go about setting the idle mixture on the Hiller UH12E twin carb set up.

This is about the hardest Helicopter to adjust, so therefore most other machines can use the same basic system for a single carb installation.

 

Safety Notes:

 

This procedure involves disassembly of the throttle controls and therefore requires a duplicate inspection of the re-assembly of these controls before further flight.

 

A qualified pilot and aircraft maintenance engineer are required for this procedure in Australia

 

A briefing between the pilot and engineer must be carried out before commencing this adjustment. Each must understand the sequence of events and any emergency procedures

 

The engineer must have adequate hearing protection due proximity of the exhaust pipes

 

DO NOT use this procedure in high wind conditions due low rotor RPM (blade flapping)

 

Be aware of the effects of local conditions AMSL.

 

At all times, the manufacturer’s M/Overhaul manual and the Civil Aviation Regulations have precedence over this advice and must be complied with.

 

Work Instructions(UH12E):

Read before commencment:

	Fly one circuit to warm the whole helicopter to operating temperature (reduces engine internal friction)
	Land, cool down and shut the engine off.
	Throttle friction to full OFF
	Using appropriate tools, remove the split pin and then the nut and clevis attaching the throttle cable to the carb throttle arm (note which attach hole the clevis pin is in)
	Restart the engine with the engineer ensuring that the Carb throttle arm remains fully against the idle screw.
	With a screwdriver, wind out the throttle idle stop while maintaining pressure on the throttle arm to close the carb butterfly valve. Bring the engine revs down to 900 – 1000 RPM. (Yes, it will sound rough and clunky)
	Identify and slowly screw in the large carb idle mixture screw on the side of one carb until the engine runs rougher.
	Screw it out again until it seems smoother and then back in until the engine starts running rough again.
	Stop at this point and note the position of the slot on the idle screw.
	Then screw the idle mixture screw out exactly two turns.
	Do this same procedure on the other carb.
	Then – DO IT AGAIN on BOTH Carbs.
	The idle mixture is now set.
	Set the idle speed at 1650 RPM (50% aprox) and shut down the engine with the mixture control.
	Reconnect and carry out a duplicate inspection of the throttle assy.
	Restart the engine, check that full closed throttle on the collective is actually caused by the idle stop screw on the carb and not anywhere else in the control run.
	Check that the minimum engine idle speed is still 1650 ERPM, carb heat cold.
	Run the engine to 3000 RPM and smoothly close the throttle to check for correct needle split. DO NOT snap the throttle shut as this is detrimental to the engine crankshaft assy.
	Notate the aircraft logbook where appropriate.
	Congratulations – you should now have an engine that is set for better starting in your current ambient conditions.