American horizontally opposed engines can catch out the unwary (or forgetful): the Lycoming No 1 cylinder is right-hand front but the Continental No 1 is right-hand rear.
Ground runs are interesting if you time the magnetos to the wrong cylinder. :confused:

I suppose this thread is as good a reason as any why turbine enjines dominate.

Piston aircraft engines , the big ones anyway seem to anon mecahancal engineer like me almost unworkably complicated -machining crankshafts for things like a DC7 or Stratocruiser engine must have been a nightmare and an incredible challenge for the machinists - no ultra precise computer controlled machines in 1953 I am sure

No wonder as a kid I seemed to see about one gently windmilling feathered engine a day as the big props roared out of LHR ( I grew up right next door) Mind you what a great noise they made and what a great sight at night
PB
Excuse the thread drift

Do bear in mind tha the largest output of the big piston engines took place during WW2, when they were assembled by, predominantly, women taken from non-engineering backgrounds, and put together in factories (in the UK at least) with restricted lighting and subject to constant risk of bombing.

The reliability of these complex engines in these circumstances is thus extraordinary - although looking at the Wright R-3350 fitted to the B-29 (and later Lockheed Constellation and others) the failure rate was such it was unusual for them to get beyong a few hundred hours. I believe the engines fitted to the B-29s used on the atomic bomb runs had been specially manufactured to enhanced tolerances and subject to much special testing before delivery.

i read many years back that HERMANN GORING knew the war was lost the first time he saw the build quality of the radial engine in a shot down B17.
he realised his economy (at the time-1942,he was still the head of the 4 year plan) could not afford a similar engine in a "disposable" aircraft!!!

As i remember it the mags we used [Bosh] I think ,had a "cog" type wheel to operate the points with a Red Dot on the master "tooth" we turned the engine till the points were open at the top of the master cam and adjusted this to 10thou +or_1 this was done in the hanger dock on check 2,3,and4s with all the plugs removed this was easier than the old 6in rule across the back and setting this to just opening using a timing light far to time consuming [they were both approved methods ] we were lucky except for DB, and XL [both EX Dart Daks ] B.E.A. modded our engine firewalls to have access panels fitted so setting up was a simple job not having to mess about with mirrors to see what you were doing.

DId the Stratocruiser engines have ignition analisers ?[pardon spelling]the thought of changing 28 plugs is too much to bear for a "MAG DROP] 14 was bad enough our Elizabethens Bristol engines had it and it gave you on a scope the "duff" plug or cylinder.:)

Correction - Wasp Major, 28 cylinders, 56 sparkyplugs. :ugh:

Oh Dear
 

Not wishing to nit pick 28 pots, 56 plugs ,2per cylinder ,left and right hand mags each firing 1 plug per cylinder ,mag drop checked by switching each mag off in turn check rev drop is with in limits ,thus ONLY?having to change 1 bank of plugs , normal for most piston engines on ground run up check before take off but still the height of tedium for the engine fitter and the electrician as he had to do a H.T.Insulation check on the ignition harness as well ,quite a lively task when it was raining or when it was damp [kept the old Heart going with the shocks]:) Sorry when I said 14 I was talking about the Double Wasp

One short cut was to let the engine cool down and then start & run on the mag with the drop. After shutdown, the cold cylinder indicated the u/s plug or lead. Removing and refitting the cowlings was always a pain if you were doing the job downline without proper stands.

Hence the "Magic Wand" which was a thermocouple on a longish pole.

Start a cold(ish) engine and run for a couple of minutes, then touch the wand on each plug. With a bit of luck one or more will be cold and problem solved.

stevef is right about the "fun" of this stuff away from proper work stands!

So, 4 engines on a Stratocruiser, 224 spark plugs. Goodness me, did they ALL have to be changed/spark gap tested on a check ? However long did that take ?

B.O.A.C. Spark plugs Inc
 

Though I had left B.O.A.C.to serve King and country [National service ]
before the Strat came in, they had a special section which all they did was service spark plugs, operated by Demented chaps, who to stop them escaping were chained to their benches. With a fleet of Yorks, Lancs, Connies Dc4M2s And the Strat they serviced 1000s of plugs per year plus of course all the lads car and motor bike plugs for a small fee.:ok:

WHBM,

It took about 5 minutes less than forever. When something like a Guppy dropped in with an engine problem a compression check on all 4 engines (wrong spec fuel - not 115/145 as required) was worth a couple of days for the engine crews. Then, of course, at least 1 plug would snap off in the cylinder head. Try to have a nice day!! OTOH, the overtime was usually welcome to us poor ground engineers!! :ok:

On our first Daks the points were accessed by removing a the cover on the back of the mag and then you had a 3 inch gap to the firewall with which to adjust the points with the aid of a mirror :ugh:

Later aircraft had a big panel in the firewall and you could adjust the points standing on the mainwheel
Luxury :}

Avionics.
Yes we had the dreaded plug bay and also a lifejacket bay
Both manned by errant apprentii :uhoh:

:) (presumably :mad: initially !)

Could you drill it out without removing the cylinder ?

These foolish things
 

So glad "Got the T-shirt " enjoyed the good fortune of access to the mags from the u/c bay I thought the access panels was a BEA mod perhaps they were the Daks we sold later in the late 50s early 60s, did he have the missfortune as the P.W was a bit of an oil thrower to stand on the wheel and slip into a heap onto the floor scattering screwdriver and feeler gauges to the 4 winds? [I hope I wasn't the only one] :hmm:

The Cessna 190/195 was even tighter - but Cessna designed the engine mount so the whole engine would hinge out on one side, and the mag covers & points were then easily reached.

Worst I ever worked on was the Howard DGA - about 1" clearance mags to the firewall. (There were firewall access covers, but they were useless because the rudder pedals were in the way. :ugh: )

We found the easiest & fastest way was to pull the entire firewall forward for easy access. :eek:

Then, of course, there was the B36. Wonder how long a plug change took.


After an excellent landing you can use the airplane again!

WHBM,

The technique my mob used was to bring the relevant cylinder to TDC, insert an air hose adapter into the good plug hole and set a relatively gentle air flow into the cylinder. This would, naturally, ensure that air was flowing out of the plug hole with the remains of the plug jammed in it - they generally broke off close to flush. It then remained for the poor victim to grind down a hacksaw blade to fit, jam the other end of it into a bit of scrap hydraulic hose so you didn't carve up your hand and cut to the TOP of the cylinder thread. Then make another cut about opposite and the final cut, very carefully, about 1/4 inch from one of the others. The master plan was to grab the small segment with long nose pliers and twist it out. After that it was fairly easy to grab one of the sides and gently fold it in a bit to enable the remains to be pulled out.

Should anything drop into the cylinder you had all the fun of a cylinder change and some terse words from the foreman. You could usually get away with a new Helicoil if the plug thread was damaged.

Ah yes, the Good Old Days with a few hours of smelly compressed air in your face and plenty of steel shavings to inhale, not to mention the contortions required to work on most cylinders using the usual crappy work stands. Thank heavens for jets!!

mustafgander you know you enjoyed it, all that lovely black oil ,the thrill of the slipstream in the hair [if you had any after removing broken plugs ]ajusting the vacum pump ,retrieving the engine bearer bolts and anything else you dropped from the mess in the drip tray , come on the jet boys had no fun at all. The odd pint of oil top up the to the max not 50 to 100 gallons [if the engine didn't use much oil there was something wrong ]also the up side was petrol was in the low thousands of gallons on the big birds and 100s on the Dak instead of the hours spent refuelling 747s one could take War and Peace to read whilst refuelling those . I know it's rose tinted glasses time but it could be fun ,we were younger then.