Interesting question…but surely it is just chance.

If two engines are running at roughly the same RPM the relative RPM between them must be low…

…and since at three points in every revolution the blades will adopt the same orientation they will ‘synchronise’ fairly often. And if the relative RPM is low they will tend to stay roughly synchronised for much of the time.

Just my guess. 🙂

Your correct, the relative positions of blades is a coincidence. It’s the rpm of the engines which is being sync’d, therefore the audible frequencies of each engine which are the same and not competing. Like tuning a stringed musical instrument, there is an anoying beat tone interference wave pattern clearly audible, as one string approaches the same frequency as its reference, warbling away until the same note is achieved.

Actually quite prophetic.

The caption talks of the forthcoming London Flypast of 20th September. It doesn’t say the year but logically it is 1959.

TE476, the Spitfire in the photograph, bellied in at Martlesham Heath on the 12th September 1959, to be grounded for some 36 years.

SL574, the other BBMF Mk XVI, performed the Flypast on the day, the 20th September, and bellied in on the OXO sports field at Bromley, never to fly again.

Mark

The caption is dated 24/08/59 Mark12 (bottom right), your spot on.

ps, what is a picture of the most up to date RAF aircraft doing in the Historic Aviation forum?

Because, after its very lengthy birth, by the time it came into service it was a historic aircraft! :diablo:

‘Vulcan knockers’, do your self a favour.

Have a day off.

Mark

I agree, change the record please children…..

Vulcan doomsters, you have a pm facility at your disposal for your DOOMSTER conversations with fellow Vulcan DOOMSTERS. The rest of the world doesn’t need to hear your constant WHINEING at the moment thanks very much.

Your in danger of ruining Moggies very special day 😀

I think possibly they were pulling your leg

Starting a Bristol Hercules radial by handswinging is a definite non-starter 😀

However turning the engine over by hand before starting is normal procedure on big radials to avoid damage from hydraulic lock.

Courtesy Steve Curry – Radial Engines Ltd

Moggy

I always find this standard partial explanation trotted out a bit lacking in detail WRT to ‘avoiding a hydraulic lock’:

If a sufficient quantity of oil had pooled in a lower cylinder, enough to in fact cause a hydraulic lock, wouldn’t the act of pulling through TDC with the signifcantly superior mechanical advantage of a long blade (lever) through a reduction gearbox, than the starter, almost guarantee a bent rod?

Perhaps the act of pulling a blade through, identifies if a lock is occuring thus allowing the option to pull the plugs and drain before actually pulling through TDC, rather than risk using the starter to take a run at it without checking first?

Does the act of pulling through a few blades as well as identifying if a lock is going to occur, disperse excess oil that might not be sufficent to cause a lock, but perhaps make the starting a little difficult?

How easy is it to detect the load via the end of a blade where there is a hydraulic lock about to occur as opposed to just a normal pull through?

Further answers for more clarity please radial engine operators 😀

Does anyone know if a time expired Bulldog airframe (being a fatigue life design certification) could have the expired components replaced and the airframe zero houred if the original design authority backed it? This is obviously a paper work problem as opposed to an engineering problem. Seems a shame to life these and not a dodgy flying club C152.

I think I heard that time expired Robinson R22’s can go back to the factory for a re-build to zero hour the paper work or otherwise are on paper scrap.

Nice…

Anyone got a simple schematic of the wing – I’d be very interested to see how they designed it with only one spar! Common design rules dictate that the wing would flex around its lateral axis (Unless of course I misunderstand the concept….)

I have a few old aviation books which cover the assembly of a monospar. I’ll scan an image or two of the arrangment when I get a mo.

As I recall (TBC) it has a lot of wire rigging. Bracing takes the form of single struts projecting perpendicular from the fore and aft of the spar web, along the middle of the spar from root to tip. Each single strut forms the apex of a pyramid with four bracing wires projecting back to the top and bottom spar webs. These pyramids of wires sit side by side and work together as well as with the similar arrangment forwards of the spar. It makes a lof more sense when you see it, but it is very tortionally rigid as a result, thus negating a functional rear spar member.

How difficult would it be to build these to faithfully replicate the two types in terms of the experience and make them a useful training tool?

Have you seen this one David?

http://www.simhardware.org/index.html