Merlin/Griffon Question

[Oscar Duck]

As the man said ; there is no subsitute for cubic inches..

Griffon Spits rule...

[Christer]

Bill,
there was no Spitfire built with a Griffin but several with a Griffon ... ... sorry, but I have been sitting on my hands for two days now ... ... !

On a more serious note, I did a quick count in "Spitfire - The History" by Morgan/Shacklady and the number of Griffon powered Spitfires are:
110 Mk XII
957 Mk XIV
300 Mk XVIII
225 Mk XIX
120 Mk 21
263 Mk 22
78 Mk 24
which gives a total of 2053.

I didn't count the Merlin engined variants ... ... but multiplying the above total by 10 would give a fair approximation (for comparison).

About the effects of a rotating propeller, this discussion has confused me. I thought that I knew the following:

Torque gets the propeller rotating and the airframe rolling in opposite directions. A Merlin Spit torque rolls to port and a Griffon Spit torque rolls to starboard. (I have a Mk XIX manual from the Swedish Airforce and it states that the oleo in the starboard side landing gear has a higher pressure than the one on the port side to prevent it from compressing fully by the torque effects on take off.)

The slipstream, hitting the fin on one of the sides makes the aircraft yaw. A Merlin Spit to port and a Griffon Spit to starboard.

In level flight, there is no P-factor because the thrust line and the line of flight are the same. When climbing, the increased Angle of Attack gives an increased AoA to the downwards going propeller blade and a decreased AoA to the upwards going propeller blade. This gives an "out of trim" like situation which is not as severe as the slipstream effect but it acts in the same direction.

Then there is the precession effect which made pilots hate rotary engines but let's forget about that one (my brain hurts).

Now someone, please, tell me if I'm right or wrong!

Christer

[Richard Woods]

Talking to a friend who works on Merlins and Griffons, he says they rotate different ways round.

He also says the torque of the Griffon is such that if a pilot went for full power straight from nothing, it would make the Spitfire do a neat little roll and end up on its back.

Regards

Ric

[Bradburger]

Everybody is focusing on the variations. What I was hoping was somebody might have production numbers or at least a close estimate of how many Spitfires were built with Merlins and how many with Griffons? All the Merlin Spits turn the same way as US planes, thus the column in AOPA is mostly incorrect when it talks about turning the opposite.

Bill,

Maybe this is what you are looking for?

Below is a breakdown of ALL Spitifre Marks built, taken from the excellent Harleyford book 'Spitfire - The Story of A Famous Fighter' by the late Bruce Robertson.

----------------------------------------------------------------------

SPITFIRE MARKS PRODUCTION NUMBERS

MK I - 1566 (1516 Supermarine, 50 Westland)

MKII - 920 (CBAF*)

PRVI - 229 (Supermarine)

MKV - 6479 (1367 Supermarine, 4477 CBAF, 635 Westland)

MKVI - 100 (Supermarine)

MKVII - 140 (Supermarine)

MKVIII - 1658 (Supermarine)

MKIX - 5665 (561 Supermarine, 5104 CBAF)

PRX - 16 (Supermarine)

PRXI - 471 (Supermarine)

MKXII - 100 (Supermarine)

MKXIV - 957 (Supermarine)

MKXVI - 1054 (CBAF)

MKXVII - 300 (Supermarine)

PRXIX - 225 (Supermarine)

MK21 - 122 (CBAF)

MK22 - 278 (16 Supermarine, 262 CBAF)

MK24 - 54 (Supermarine)

TOTAL - 20,334

*Castle Bromwich Aircraft Factory

-----------------------------------------------------------------------
Cheers

Paul

[Bill Greenwood]

Guys thanks for all the good information. To round off it seems about 2000, of the almost 23,000 Spits, land and sea, built were with Griffons. So I will write AOPA the clarification, that most Spits, the other 21,000 were Merlin engined and turn the "right" way, same as a Mustang. The other part they had a bit off was that you needed to stand on the rudder to keep it straight on takeoff. Not true at all in the 3 Merlin ones have flown, At normal takeoff power of 7 lbs boost, 44 inches 3000 rpm, with full right trim you only need partial right rudder. I don't use full trim, and still I am only holding about 1/2 rudder. If you get over 8lbs, or jam the power on at low speed you begin to run out of control. I have also read one has to be more gentle with the Griffon models due to the extra power, but it doesn't seem to be a problem for anyone. And they get off the runway pretty quickly in any case.

[dhfan]

There are somewhere in the region of 800 Griffon powered Seafires to add to the total.

[Bradburger]

There are somewhere in the region of 800 Griffon powered Seafires to add to the total.

O.K, here's the entire number of Seafires built, from the same source:

SEAFIRE MARKS PRODUCTION NUMBERS

MKII - 372 (262 Supermarine, 110 Westland)

MKII/III Hybrid** - 30 (Westland)

MKIII - 1220 - (870 Westland, 350 Cunliffe Owen)

MKXV - 390 (6 Supermarine, 250 Westland, 134 Cunliffe Owen)

XVII - 232 (212 Westland, 20 Cunliffe Owen)

MK45 - 50 (CBAF)

MK46 - 24 (Supermarine)

MK47 - 90 (Supermarine)

TOTAL - 2,408

** Non folding wings

Note: MKI existed only as a conversion from the MKVB's

Cheers

Paul

[Bradburger]

Bill,

Interesting what you say about how much rudder you use during take off.

It seems that quite a few current day Spit pilots leave the rudder trim neutral.

Shuttleworth chief pilot Andy Sephton is one, as he states in an article on flying the collections Spit V, that the footload can easily be held, and points out the consequences of setting it the wrong way, if you are lucky enough to fly both Merlin & Griffon powered examples!

I believe this is what caused Sir Tim Wallis to crash during take off on his first flight in his MKXIV (NH799) - he had been used to flying the MKXVI for a number of years, and automatically set the rudder trim as he did for the Merlin powered machine.

Cheers

Paul

[Bill Greenwood]

Paul, the Pilot Notes say full right rudder trim for takeoff. The main reason I don't use this anymore is if you do, as soon as you get off the ground, raise the gear, and accelerate through 100 knots you will need a lot of left rudder until you take out that trim you had in. I just back off the trim about 2 turns from full for my takeoff setting. Using 7 or 8 pounds for takeoff, I still have plenty of rudder control without much force needed. Also if you ever need to do a go around, it will be from zero trim and this way you'll be a little more tuned up for this. Really, rudder and yaw control on a Spit is no challenge. When I flew Crazy Horse with Lee in Florida, he made a point of telling me I had zero trim as we came in to land. He seemed to think this was an area of concern, but I really never noticed much of a problem, even doing a go around in that Mustang. You just have to be gradual on the power and keep the nose straight.
I'm not sure about Tim's MK 14 accident, if there are witnesses or video that shows him going off the the right. I know if I flew a Griffon one I'd be careful to set in left trim.

[bdk]

My understanding is that you cannot maintain directional control at full power in the Griffon Spit on takeoff unless it has the contra-rotating prop.

[Bill Greenwood]

BDK, you would not be able to keep a Spitfire straight at full power on takeoff, either Merlin or Griffin; but you don't need anywhere near full power. My Merlin is rated at 18 lbs or 66 inches at full power on standard fuel, with up to 25 lbs or 80 inches as an overboost on 145 fuel. Normal takoff is 7lbs, or 44 inches and it will stay with a Mustang using 50 to 55 inches. It doesn't hang about on the runway like some lard asss radial engined Battlewagon, but gets up and goes flying. At civilian weights, and 12 lbs, at 8000' elevation of my airport, it will put the VSI at 4000 fpm once the gear is up,, one of the biggest differences you notice over a regular airplane. I'm not that familiar with the Griffon Spits, but they would be similar, one has enough control for the power needed for takeoff, and once up to 90k or so you can use more power.
P. S. One disadvantage of having no ears is you can't hear the lovely Merlin.

[bdk]

P. S. One disadvantage of having no ears is you can't hear the lovely Merlin.

My ears are flush for superior aerodynamics....

I wonder how the last Griffon Spits were with that huge vertical stabilizer and rudder. I suspect that your Spit is not overpowered as much as it is under-ruddered! If you ever had to carry the fuel load of a Mustang into combat for a long range escort mission I'm sure you would have appreciated getting all the power in for takeoff.

[JDK]

Thanks Christer, I read it.

bdk. Full power wouldn't be a good idea, would it? Most Spitfires weren't carrying huge loads (wingloading and power-weight was low and high respectively, relative to other late mid-late war fighters) but see below. Hence the need for a cotraprop on the late Naval ones - track streight for an overloaded a/c on a carrier.

wonder how the last Griffon Spits were with that huge vertical stabilizer and rudder. I suspect that your Spit is not overpowered as much as it is under-ruddered! If you ever had to carry the fuel load of a Mustang into combat for a long range escort mission I'm sure you would have appreciated getting all the power in for takeoff.

Fin and rudder. Yes, I think. Also there was a hellava lot of weight up the back end to keep the nose off the ground.

The latter Griffon Spitfires had a spit trimtab (have a look for a photo) with one half about 5 degrees out, but fixed to the other half, the whole moving as one. Not sure how that worked!

Surely you'd feed in the power on t/o however heavily loaded, and thus be able to track streightish. Firewalling the throttle leads to an inverted wreck offset the side of the end of the runway?

Not that I know anything about Spitfires...

[Bill Greenwood]

BDK,JDK No Spitfire of the Merlin ones that I have flown ever seemed to lack rudder control. I have flown mine with a full 60 gal external fuel tank. In RAF service they had as large as 175 gal drop tank. The rudder on my MK IX is so effective that I can use it to taxi turn without even needing brakes if speed is 20 mph. I have fast taxied a MK XVIII with the Griffon up to about 30 mph and was surprised that it felt pretty similar. I was to fly it, but wanted a little more time to familarize myself with it, but unfortunately it was lost in a fatal accident in bad weather, so I can only speak of the Griffs on what have read and been told.
With further development Spit power grew and grew with the Griffon until the Spiteful with the three speed supercharger and 2500 hp, a brute with 494 mph top speed that may have been the peak of piston fighter progress. As power went off the chart, the rudders got larger. But I DON"T think it was so much needed for takeoff control, rather to handle the yaw forces with sudden changes in throttle and for high speed dives.

Last edited by Bill Greenwood on Sat Mar 08, 2008 10:59 pm, edited 1 time in total.

[skybolt2003]

No Spitfire of the Merlin ones that I have flown ever seemed to lack rudder control. The rudder on my MK IX is so effective that I can use it to taxi turn without even needing brakes if speed is 30 mph.

I am surprised that you would do anything but keep a very cautious straight path at anything above walking speed. The rudder might be up to it, but it seems like physics might take over (I know it would-has-in my more pedestrian ship)