DCS: Spitfire Mk LF IXc Discussion

[Friedrich-4B]

I observe that the tougher Merlin 66 series pistons failed in as little as 7 1/2 hour stress load acccording to the stress test results posted. Even the toughest ones did not last longer than 50 hours.

 

I wonder what the lifespan of the less tough Merlin II/III's pistons could have been then.

 

I also wonder what sort of requirement R-R had in mind before clearing a rating for use, as it cleared +18 lbs while the pistons kept failing under 10 hours of stress at the said load.

 

If Kurfurst is referring to Fig. 28 of Lovesey's article, nowhere does the chart or Lovesey's text say that the pistons "kept failing" after 10 hours of stress testing (ie: continuous running at +18 pounds and 3000 rpm). On reading available material (see below), Rolls-Royce did not clear "+18 lbs while the pistons kept failing under 10 hours of stress at the said load" because they tested and altered the piston's design (and the crankcase and other vital components) until it wasn't failing at the low limits claimed.

 

What the article does point out is that "some ring gumming" occurred after 7 1/2 hours during one test (plus four other tests ranging from 9 1/2 hrs to 50), without stipulating whether this was enough to cause a serious loss of compression, or how many piston rings were affected and to what extent.

 

 

As it is, the tests for the Merlin 66 referred to occurred between November 1942 and April 1943; as noted by Alec Harvey-Bailey in The Merlin in Perspective - The Combat Years (Rolls-Royce Heritage Trust, 1995) pages 67 & 68, piston rings gumming up and other piston-related problems were solved in production Merlin 66s:

 

 

Thus, the DCS Merlin 66 of 1944 shouldn't have pistons gumming up, or have other piston related problems after a mere 7 1/2 to 50 hours of running at +18 lbs @ 3,000 rpm.

Edited November 12, 2015 by Friedrich-4/B
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[MiloMorai]

I observe that the tougher Merlin 66 series pistons failed in as little as 7 1/2 hour stress load acccording to the stress test results posted. Even the toughest ones did not last longer than 50 hours.

 

I wonder what the lifespan of the less tough Merlin II/III's pistons could have been then.

 

I also wonder what sort of requirement R-R had in mind before clearing a rating for use, as it cleared +18 lbs while the pistons kept failing under 10 hours of stress at the said load.

 

Be careful what you wish for Kurfurst.

 

Daimler-Benz DB 605: "... I should point out the enormous problems caused by the unreliability of our supercharged Daimler-Benz 605 AS engines. They would barely make it beyond the fateful 50 hour mark. We were astonished to read in 'Interavia' that the Russians had complained to the Americans that the engines that had been supplied had a life of only 300 hours instead of the 350 hours promised! In my Staffel, it was frequently the case that engines would have to be changed two or three times before finding one which ran satisfactorily ..." - Karl Mitterdorfer, JG 300

[NineLine]

How many people fly their DCS Module 50 hours straight without logging out of the sim? Not sure engine life span is anything we need to worry about right now, we get a factory fresh one each time we play.

[Wolf Rider]

let alone the possibility of 50 hours (two days/ nights) of flight without adequate capacity (bearing in mind air tankers weren't about then) for fuel to keep the bird in the air all that time?

[Flamin_Squirrel]

let alone the possibility of 50 hours (two days/ nights) of flight without adequate capacity (bearing in mind air tankers weren't about then) for fuel to keep the bird in the air all that time?

 

The 50 hours refers to total running time, not continuous running time.

[Cripple]

How many people fly their DCS Module 50 hours straight without logging out of the sim? Not sure engine life span is anything we need to worry about right now, we get a factory fresh one each time we play.

 

Pity. I rather like the idea of modelled engine life-span... I think one of the other Spitfire Sims does it. You have to remember to put the kite in for maintenance and all that.

[TwilightZone]

Pity. I rather like the idea of modelled engine life-span... I think one of the other Spitfire Sims does it. You have to remember to put the kite in for maintenance and all that.

i used to love this feature with the A2A spitfire in FSX. fun to see how many days, months etc. you could keep the engine going without major maintenance......of course no guns on that spit.....:(

would be great though, even as a off or on option in DCS:thumbup:

[Kurfürst]

How many people fly their DCS Module 50 hours straight without logging out of the sim? Not sure engine life span is anything we need to worry about right now, we get a factory fresh one each time we play.

 

I doubt if many of the planes themselves lasted for 50 hours in real wartime conditions anyway... ;)

[Rogue Trooper]

As a Brit it will be so interesting when all this technical information becomes a reality in DCS, will she be what I expect?

Will she disapoint me?

Will she be an amazing warts and all rendition?

I cannot wait to find out!

[Wolf Rider]

 

The 50 hours refers to total running time, not continuous running time.

 

 

 

 

 

If Kurfurst is referring to Fig. 28 of Lovesey's article, nowhere does the chart or Lovesey's text say that the pistons "kept failing" after 10 hours of stress testing (ie: continuous running at +18 pounds and 3000 rpm). On reading available material (see below), Rolls-Royce did not clear "+18 lbs while the pistons kept failing under 10 hours of stress at the said load" because they tested and altered the piston's design (and the crankcase and other vital components) until it wasn't failing at the low limits claimed.

 

~

 

 

 

Is something being confused somewhere?

[Crumpp]

Is something being confused somewhere?

 

Yep...

 

:music_whistling:

 

That is why some folks think the operational limits published in the POH are just a big joke to fool the pilots going into combat.

[Yo-Yo]

Yep...

 

:music_whistling:

 

That is why some folks think the operational limits published in the POH are just a big joke to fool the pilots going into combat.

.

 

By the way, I just read a lot of ping-pong conversation about how to set this max aft CoG for Spifires... :) with and without inertial bobweights. I can say that it was oriented for pilot skill (one pilot could not react for hinge moment reversal at high AoA and G, the second with beter reaction and skill could do it...).

[Crumpp]

Yo-Yo says:

I can say that it was oriented for pilot skill (one pilot could not react for hinge moment reversal at high AoA and G, the second with beter reaction and skill could do it...).

 

Oh absolutely! :thumbup:

That is the personality of the Spitfire.

The experienced pilots who were used to the longitudinal instability love it. In fact, many complained when the bob-weights were added saying it ruined the "feel" of the aircraft.

 

 

 

The heavy buffet, short stick travel, harsh accelerated stall, and longitudinal instability will have those new to the type complaining that you "porked" the airplane.

 

Experienced players will come to appreciate some of those characteristics which help to stay in the envelope or contribute to the maneuverability. They will find they have the best level turning aircraft on the western front and an excellent dog-fighter in their hands.

 

That is the dichotomy of the Spitfire and why it is discussed in Stability and Control engineering classes. Characteristics that in isolation are not that desirable combine in such a manner as to play off each other creating an end result that is desirable.

 

It is like a beautiful woman and must be caressed around the sky to perform its dance! :smilewink:

 

Something most pilots get used to in 10-20 hours of flying it.

 

I am guessing, but I think players in DCS will like the increased stick force per G. If you implement it like the Bf-109K4, it will slow the stick acceleration increasing control.

Edited November 16, 2015 by Crumpp

[NineLine]

Hmmm, so will we get extra options then? :)

[Crumpp]

I think what he means is that the instability was divided by pilot opinion.

[NineLine]

I think what he means is that the instability was divided by pilot opinion.

 

Yeah, understood that, but wonder if that means we will get options to set that in sim.

[Yo-Yo]

Oh absolutely! :thumbup:

That is the personality of the Spitfire.

The experienced pilots who were used to the longitudinal instability love it. In fact, many complained when the bob-weights were added saying it ruined the "feel" of the aircraft.

 

 

 

The heavy buffet, short stick travel, harsh accelerated stall, and longitudinal instability will have those new to the type complaining that you "porked" the airplane.

 

Experienced players will come to appreciate some of those characteristics which help to stay in the envelope or contribute to the maneuverability. They will find they have the best level turning aircraft on the western front and an excellent dog-fighter in their hands.

 

That is the dichotomy of the Spitfire and why it is discussed in Stability and Control engineering classes. Characteristics that in isolation are not that desirable combine in such a manner as to play off each other creating an end result that is desirable.

 

It is like a beautiful woman and must be caressed around the sky to perform its dance! :smilewink:

 

Something most pilots get used to in 10-20 hours of flying it.

 

I am guessing, but I think players in DCS will like the increased stick force per G. If you implement it like the Bf-109K4, it will slow the stick acceleration increasing control.

 

 

I am going to show some more docs as soon as they are arranged, processed and sorted... but the reading was very interesting, though I was very short in time.

Anyway, the feelings and opinions of different pilots could be very different. For example, as I asked Erich about 109G stability he said that he did not find it unpleasant, though Rusian test pilots mentioned the instability as disadvantage of 109G (though I-16 had even worse instability or was neutral having worse damping due to its short fuselage). Possibly, it was done not to praise German plane...

 

 

Additionally, pilots complied to unwanted reaction during landing and taxiing because of this bobweight.

Edited November 16, 2015 by Yo-Yo

[NineLine]

I am going to show some more docs as soon as they are arranged, processed and sorted... but the reading was very interesting, though I was very short in time.

Anyway, the feelings and opinions of different pilots could be very different. For example, as I asked Erich about 109G stability he said that he did not find it unpleasant, though Rusian test pilots mentioned the instability as disadvantage of 109G (though I-16 had even worse instability or was neutral having worse damping due to its short fuselage). Possibly, it was done not to praise German plane...

 

 

Additionally, pilots complied to unwanted reaction during landing and taxiing because of this bobweight.

 

Thats the problem with pilot reports though, they are very personal to that individual. Of course Erich spoke fondly of the 109, it was his home for most of the war :) Now take someone unfamiliar with the 109, throw them in it and you have all the users complaining about trim tabs :D

 

I am sure its the same with the Spitfire.... new pilot vs vet pilot with describe the aircraft differently... anyways cant wait to see all you came up with on your little trip :)

[Friedrich-4B]

Additionally, pilots complied to unwanted reaction during landing and taxiing because of this bobweight.

 

Not that the Spitfire IX used a bobweight for the elevator; that was a feature of some Spitfires with the "small" elevator...

[MiloMorai]

What does a Mk V have to do with the Mk IX?

 

Note that it was 5 minutes for both the 18lb boost and the 25lb boost Merlin engine.:shocking:

 

There was NO source given for the graphic posted in Post #813.

[DD_Fenrir]

What does a Mk V have to do with the Mk IX?

 

Note that it was 5 minutes for both the 18lb boost and the 25lb boost Merlin engine.:shocking:

 

There was NO source given for the graphic posted in Post #813.

 

Crummps legendary refusal to acknowledge the difference between a MkV and MkIX thats the difference!

 

Oh and the "fact" that neutral stability is the same as instability in his book. :doh:

[Yo-Yo]

Not that the Spitfire IX used a bobweight for the elevator; that was a feature of some Spitfires with the "small" elevator...

 

It was feature of Spitfires having CoG up to 8.6" aft datum that was close to neutral point. For example, Mk V. Typical Mk XI position of CoG was 4-5 inches.

[NineLine]

What does a Mk V have to do with the Mk IX?

 

From what I understand lots, especially the earlier IX models.... but Yo-Yo would be able to comment more.

[MiloMorai]

From what I understand lots, especially the earlier IX models.... but Yo-Yo would be able to comment more.

 

Is this a confirmation that the Spitfire IX we will be getting is an early Mark?

 

Oh well, another early 1944 Allied airplane to 'fly' against late 1944 Luftwaffe airplanes.

[NineLine]

Is this a confirmation that the Spitfire IX we will be getting is an early Mark?

 

Oh well, another early 1944 Allied airplane to 'fly' against late 1944 Luftwaffe airplanes.

 

Sooooooooo what? :pilotfly:

 

Even if it is an earlier IX, which seems it is just by looking at the model we have seen... I am sure it will be fine, you probably wont be an instant ace... might need to practice and get good, but you will be fine I am sure...