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[Sutts]

Originally Posted by Robo.

R.M.3.S. is stating +12lbs. as Combat Power Rating for the Merlin XII - 1280hp/3000rpm/10500ft/+12 lbs.

+12.lbs was only possible with BCC-O engaged anyway as far I know.

Take-off power was stated as 1175hp/3000rpm/+12.5 lbs

Perhaps they considered the BCC-O as maximum power hence CPR in the manual. I am sure the manual deals with the limits of the usage and reporting / justifying it's use in combat. +12lbs @ 3000rpm was maximum strain you could ever put onto that engine. There are anecdotal stories about Spitfires (I don't know if they were Merlin XIIs or IIIs tbh) scrambling to intercept a raid at some important target in Lodnon. 6 took-off, BCC-O used straight away to climb asap. The result was that some had to turn back with failures and all of them needed overhaul I suppose. I'll try to dig that story as I might be wrong with details.



Agreed completely, that would be great!

Thanks Robo, I'd really like to see that story.

Do you find it strange how they'd allow 12 Lb boost for 3 mins on take off but not in combat when the pilot's life and aircraft were at risk? Am I missing something? Does 12 Lbs boost at ground level put less strain on the engine?

[41Sqn_Banks]

Originally Posted by Sutts

Thanks Robo, I'd really like to see that story.

Do you find it strange how they'd allow 12 Lb boost for 3 mins on take off but not in combat when the pilot's life and aircraft were at risk? Am I missing something? Does 12 Lbs boost at ground level put less strain on the engine?

Source: AP 2095 Pilot's Notes General (1st Edition, 1941)

[Sutts]

Originally Posted by 41Sqn_Banks

Source: AP 2095 Pilot's Notes General (1st Edition, 1941)

Thanks

[pupaxx]

Here is a link about a restored spitfire
http://www.telegraph.co.uk/history/w...-71-years.html
accordly to the serial number P9374, the machine was built by Supermarine (contract n° B980385/39) in a batch of 181 machines all MkI.
The Air Restoration Company (http://www.arc-duxford.co.uk/)sited at Duxford airfield restored the plane.
my ask is: maybe some of them for sure well know about engine limitations, they took it in flight after 70 years (I dont know who is the pilot)
Some of this community with a better knowledge of english than me can contact those guys and ask for more infos!
cheers

[Sutts]

Originally Posted by pupaxx

Here is a link about a restored spitfire
http://www.telegraph.co.uk/history/w...-71-years.html
accordly to the serial number P9374, the machine was built by Supermarine (contract n° B980385/39) in a batch of 181 machines all MkI.
The Air Restoration Company (http://www.arc-duxford.co.uk/)sited at Duxford airfield restored the plane.
my ask is: maybe some of them for sure well know about engine limitations, they took it in flight after 70 years (I dont know who is the pilot)
Some of this community with a better knowledge of english than me can contact those guys and ask for more infos!
cheers

Restored aircraft operating today will almost never use maximum boost as it would risk a rare and expensive asset unnecessarily. Many don't even have an operational turbo/super charger for ease of maintenance. I think 20,000 feet would be considered high when operating warbirds these days.

Shame as the data would have been incredibly useful.

[klem]

From Hurricane MkI Pilots Notes, Melrin II or III engine. This is a May 1941 edition - I haven't found an earlier one yet so it is possible that the combat advice differed during the BoB. I'll re-check the Library. However, the engines were the same.

[Sutts]

Originally Posted by klem

From Hurricane MkI Pilots Notes, Melrin II or III engine. This is a May 1941 edition - I haven't found an earlier one yet so it is possible that the combat advice differed during the BoB. I'll re-check the Library. However, the engines were the same.

Interesting stuff Klem, thanks for posting.

I find it quite hard to overspeed my prop - certainly not to 3600 RPM. Is there any situation on CloD where that kind of overspeed is possible?

[Robo.]

Originally Posted by Sutts

Interesting stuff Klem, thanks for posting.

I find it quite hard to overspeed my prop - certainly not to 3600 RPM. Is there any situation on CloD where that kind of overspeed is possible?

Not with the Rotol equipped Hurricane, these limits were set to the engine in general - Merlin II and III. Following airscrews have been fitted on Hurricanes of that era: Weybridge fixed pitch, de Havilland 2-pitch or Rotol constant speed. With the first two, you could indeed overrev your engine in a dive, hence the limit set in the pilot's manual. You will be able to overrev your engine in the sime flying de Havilland Mk.I fighters (Spitfire Mk.I and DH-20 Hurricane Mk.I),

klem - I do have great copy of Hurricane Mk.I pilot notes and maintenance manual dated March 1939, all pre-BoB Merlin II and III related. Great stuff, PM me if you'd care for a copy.

[Sutts]

Originally Posted by Robo.

Not with the Rotol equipped Hurricane, these limits were set to the engine in general - Merlin II and III. Following airscrews have been fitted on Hurricanes of that era: Weybridge fixed pitch, de Havilland 2-pitch or Rotol constant speed. With the first two, you could indeed overrev your engine in a dive, hence the limit set in the pilot's manual. You will be able to overrev your engine in the sime flying de Havilland Mk.I fighters (Spitfire Mk.I and DH-20 Hurricane Mk.I),

klem - I do have great copy of Hurricane Mk.I pilot notes and maintenance manual dated March 1939, all pre-BoB Merlin II and III related. Great stuff, PM me if you'd care for a copy.

Thanks Robo, I forgot it wasn't a constant speed prop on these early machines Dohhh! The reason I ask is that I've seen reference to overspeeding props in manuals for aircraft with constant speed units fitted and was wondering under what circumstances an overspeed could happen.

I guess slamming the throttle to max when going into a dive might not give the constant speed unit time to adjust?

[Robo.]

Originally Posted by Sutts

I guess slamming the throttle to max when going into a dive might not give the constant speed unit time to adjust?

Exactly.