Auto revs

Rotor Research Helicopter Info Site

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"Give 'er a few more Auto Revs Mate".

A golden rule I always obey, is to flight check any helicopter I may have to fly.

First I need to "feel" and confirm how much grunt (engine power available) it has and - secondly - how it controls (rigging) and/or vibrates (track, balance, engine, tail rotor).

If these are acceptable for the type of machine the third step is to check it’s Rotor Revs in autorotation for the values determined by the manufacture.

Many pilots have never been told of the actual in flight requirements of their helicopter type to determine what RPM the Rotor should stabilize at in autorotation under various weights and ambient conditions.

Here's how to check your Robinson R22 system.

	Find the basic empty operating weight in the flight manual - you should already know this!
	Accurately determine the operating weight - including, fuel, people, accessories etc.
	Fly the aircraft to stabilise in level flight at 65 knots at 1,500 ft above the airfield (set Altimeter @ 1013mb).
	Carry our your H.A.S.E.L. checks including application of full carb heat to keep the engine from cooling to quickly

+·H Height is appropriate above the ground for the maneuver to be performed

·A Area around is clear and safe for the maneuver – includes ground contact area if included

·S Security of self, crew and no loose objects in the cockpit or that might foul the controls, set control frictions as required

·E Engine is readied for the maneuver (stabilise cylinder head temps), sufficient fuel, mixture as required, carb temp set

·L Lookout - checking for other aircraft around, above and below and on airfield if appropriate

	Smoothly lower the collective fully down at a steady rate, maintaining airspeed @ 65 Kts IAS , rotor revs in the green and in aircraft in balance (Do not snap the throttle shut!).
	Disengage the governor (turn off the switch)

7) With the collective now fully down and the aircraft stabilised in descent - ensure that the Rotor revs are above 95%. If Ok then:

	Snick the throttle closed to split the tacho needles and check that the engine RPM is indicating 80-90%. You are now in autorotation.
	Slowly bring the IAS back to stabilize @ 50 Kts. Keep the aircraft balanced!!

As you pass thru 1000ft Above Ground Level - note and/or record accurately (this is important) the following from the instruments:

	IAS: stable at 50 Kts
	Aircraft in balance
	Altitude AMSL @ 1013 mb
	Outside Air Temp
	The stabilised rotor RPM (eg: 100%).

10) With the collective still down, smoothly (don't rush) open the throttle to join the engine and Rotor RPM together in the green.

11) Engage the governor (switch it back on). Caution: Do not overspeed engine or underspeed rotor for power on conditions

Reselect 60 Kts attitude and smoothly raise the collective to maintain or increase your altitude using cruise or climb power.

13) Congratulations - you now have the required accurate data to be checked against the autorotation reference chart located in the R22 maintenance manual. Why not check out every machine you ever fly - its too late to find out the machine has been rigged incorrectly if you have a real engine failure.

Notes:

	You must be a current, proficient pilot before attempting this test. If it is not your aircraft or you are unsure of the procedure, have it demonstrated by a competent pilot first.
	In flight aircraft balance is important - use a slip indicator or preferably- a piece of wool or light string fitted to the centre of the bubble at eye level with blue tac.
	Be accurate with your data
	A lightly loaded aircraft may have low Rotor RPM WITHOUT the Low RRPM warning horn sounding in autorotation as the collective is fully down, deactivating the low RRPM microswitch.