Avoid pro­pel­lers!

Pilot - - AIRMAIL -

I am im­pelled to re­spond to the cor­re­spon­dence in Jan­uary’s

Pi­lot and Ed Len­nox’s rant about per­sons in close prox­im­ity to pro­pel­lers on pis­ton en­gined air­craft. I have to side with Si­mon Noble on this mat­ter as it is se­ri­ous – par­tic­u­larly as Pi­lot is cer­tainly read by many young and new pi­lots who may not re­alise that pro­pel­lers are def­i­nitely to be treated with care and re­spect at all times.

The very na­ture of air­craft mag­ne­tos makes them prone to the pos­si­bil­ity of be­ing un­ex­pect­edly ac­ti­vated be­cause they are ‘live’ at all times ex­cept when earthed by the ‘P’ lead through the ig­ni­tion switches in the cock­pit. This means that if the switches are left on by the pi­lot at the com­ple­tion of the flight (a very com­mon oc­cur­rence due to the en­gine be­ing stopped with the idle cut-off) there is a pos­si­bil­ity of the en­gine fir­ing if the pro­pel­ler is moved, par­tic­u­larly if one or both mag­ne­tos are fit­ted with im­pulse units. The other pos­si­bil­ity is of one of the earth leads be­com­ing de­tached for some un­ex­pected rea­son, such as vi­bra­tion or some­times the elec­tri­cal leads be­ing in­ad­ver­tently stressed dur­ing main­te­nance lead­ing to pos­si­ble de­tach­ment later. For safety rea­sons you should check for a ‘dead-cut’ on both mag­ne­tos be­fore and after flight to de­tect a de­tached earth (P) lead.

When­ever han­dling a pro­pel­ler al­ways treat it as live. And when ac­com­pa­ny­ing non-avi­a­tion adults and par­tic­u­larly chil­dren keep them away from pro­pel­lers. There are other prob­lems as­so­ci­ated with coil ig­ni­tion on air­craft en­gines but enough is enough and safety can be main­tained by the ‘do not touch’ habit by pi­lots as well as pas­sen­gers ex­cept when nec­es­sary for pi­lots dur­ing flight op­er­a­tions.

What is my author­ity for this opin­ion? Well over fifty years as a li­cenced air­craft main­te­nance en­gi­neer and pri­vate pi­lot on sin­gle and multi-en­gined air­craft, al­though I am now re­tired. Colin Ford, Ather­ton While Colin Ford gives sound rea­son for han­dling pro­pel­lers with care, I am not sure pic­tures of pi­lots posed in close prox­im­ity to them – al­most a tra­di­tion in avi­a­tion – re­ally do en­cour­age any­one to do any­thing daft – Ed

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