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VW ‘Jack Russells’
I
have just read Steve Slater’s article about prop swinging in the April issue of the magazine. It was spot on – well informed, educational and measured. I particularly liked the comment comparing a VW engine to a Jack Russell terrier and can confirm this from my own experience of hand swinging my Nipper. It either starts first time or temperamentally after a few swings, but it never fails to surprise. Many years ago, I would swing the propeller on my own, luckily without incident, but with age and experience comes fear and caution. I was at Barton when the Luton Minor became temporarily airborne without its pilot, and I have two friends who have succumbed to serious injury through prop swinging accidents. These days, I always have my trusted prop swinger with me and I never, ever underestimate the danger of a propeller, even on my diminutive Nipper (pictured above). Kate Howe
Impulse mags and dead cuts
Brian. May I add a couple of points to Steve Slater’s comprehensive propeller swinging article? (LAA April 2020) 1. One should start on the impulse magneto ONLY. The impulse mechanism retards the spark so that kick back is unlikely to occur. If the non-impulse magneto 10 | LIGHT AVIATION | May 2020
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is on and should happen to fire, the kick back will be severe as the spark is not retarded. 2. The magneto ‘dead cut’ check when idling at the end of a flight is important to ensure the switches are operating to ground the magnetos properly. A non-impulse magneto which is not grounded, even though the switch is OFF, will likewise give a sharp kick back. This state of affairs may be indicated by no mag drop on one switch when performing the pre-flight run up, but is best checked by a momentary ‘both switches off’ at post-flight idle. One learns from experience! Yours, Rupert Hibberd.
Brake check and vacuum pumps
Just read the LA article on hand swinging and would like to add a couple of suggestions. It did not mention brakes, if they are being relied upon instead of chocks. We have got into the habit of testing brakes immediately prior to the ‘contact’ call. This involves grasping the prop near the hub and pulling forward hard to confirm adequate brake application by the ‘cockpit’ person. I’d never rely on brake latching. Also, on ‘blowing out’, it’s not advisable to turn an engine with a vacuum pump backwards (and the alternative of blowing out forwards with full throttle is too horrible to
contemplate – never trust ignition switches). However, as the types with vacuum pumps are not normally hand swung, the point is moot. Kind regards, Dave Smith.
A good purchase, at the right point
Hello Brian, I am a bit concerned about some aspects regarding the article about prop swinging, as it states that you should never wrap fingers over the trailing edge of the prop. I do not know how you can get a really good hold of the prop unless you do. I have watched people swinging props by placing their hands on the face of the prop and using friction in order to swing it. This means that a considerable forward pressure is needed into the propeller arc in order to get a good swing. This to me has always looked rather dangerous, as it means that the balance of the body is forward into the propeller arc. Using friction on the face of the prop cannot give as good a swing as wrapping the fingers round the trailing edge, and the greatest danger of not giving a really good swing is that the prop is more likely to kick back. I have watched people who are afraid of prop swinging give it gentle a swing and only just about hit top dead centre, and this is almost certain to give a kick back. I have always wrapped the first joint of April 2020 | LIGHT AVIATION | 9
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