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Spitfire Fuel Consumption/ Range test


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Hi Phil,

 

Well tested chum; been meaning to do this myself for sometime but my new arrival had been keeping me from my simming!

 

I've found a virtual version of the Mk.IX Pilots notes HERE and copy the relevant here for posterity as some of the figures I'd given in your linked thread were slightly out (particularly the WEP rate per hour) as I was posting from (an ever more fallible) memory originally.

 

54.Maximum performance

 

(i) Climbing

 

(a)The speeds in m.p.h. (knots) for maximum rate of climb are

 

Sea level to 26,000ft — 160(140) l.A.S.

26,000ft to 30,000ft. — 150(130) „

30,000ft. to 33.000ft — 140(122) „

33,000ft to 37,000ft — 130(112) „

37,000ft. to 40,000ft — 120(104) „

Above 40,000 ft. — 100( 95) „

 

(b)With the supercharger switch at AUTO, high gear is engaged automatically when the aircraft reaches a pre determined height (see para. 21). This is the optimum height for the gear change if full combat power is being used, but if normal climbing power (2,850 r.p.m. +12 lb./sq.in. boost) is being used the maximum rate of climb is obtained by delaying the gear change until the boost in low gear has fallen to +8 Ib./sq.in. This is achieved by leaving the supercharger switch at MS until the boost has fallen to this figure.

 

(ii) Combat Set the supercharger switch to AUTO and open the throttle fully. NOTE.—On those aircraft which do not have interconnected throttle and propeller controls the propeller speed control lever must be advanced to the maximum r.p.m, position before the throttle is opened fully.

 

55.Economical Flying

 

(i) Climbing On aircraft not fitted with interconnected throttle and propeller controls.

 

(a) Set the supercharger switch to MS, the propeller speed control lever to give 2,650 r.p.m, and climb at the speeds given in para. 54 (i), opening the throttle progressively to maintain a boost pressure of +7 lb./sq.in.

 

(A) Set the supercharger switch to AUTO when the maximum obtainable boost in low gear is +3 lb./sq.in., throttling back to prevent overboosting as the change to high gear is made.

On aircraft fitted with interconnected throttle and propeller controls

 

(a) Set the supercharger switch to MS. set the throttle to give +7 lb./sq.in. boost and climb at the speeds given in para. 54 (i).

 

(b) As height is gained the boost will fail and it will be necessary to advance the throttle progressively to restore it. The throttle must not, however, be advanced beyond a position at which r.p.m, rise to 2,650. Set the supercharger switch to AUTO when, at this throttle setting, the boost in low gear has fallen to +3 lb./sq.in.

 

NOTE.—Climbing at the speeds given in para. 54 (i) will ensure greatest range, but for ease of control (especially at heavy loads and with the rear fuselage tanks full of fuel) a climbing speed of 180 m.p.h. (155 kts) I.A.S. from sea level to operating height is recommended. The loss of range will be only slight.

 

 

(ii) Cruising

 

The recommended speed for maximum range is 170 m.p.h. (147 kts) I.A.S. if the aircraft is lightly loaded. At heavy loads, especially if the rear fuselage tanks are full this speed can be increased to 200 m.p.h. (172 kts) I.A.S. without incurring a serious loss of range.

 

 

On aircraft not fitted with interconnected throttle and propeller controls

 

(a) With the supercharger switch at MS fly at the maximum obtainable boost (not exceeding + 7 lb./sq.in.) and obtain the recommended speed by reducing r.p.m, as required. NOTE.— (i) R.p.m should not be reduced below a minimum of 1,800. At low altitudes, therefore, it may be necessary to reduce boost or the recommended speed will be exceeded. (ii) As the boost falls at high altitudes it will not be possible to maintain the recommended speed in low gear, even at maximum continuous r.p.m, and full throttle. It will then he necessary to set the supercharger switch to AUTO. Boost will thus be restored and it will be possible to reduce r.p.m, again (as outlined in (a) above). (iii) In both low and high gears r.p.m, which promote rough running should be avoided.

 

 

On aircraft fitted with interconnected throttle and propeller controls

 

Set the supercharger switch to MS and adjust the throttle to obtain the recommended speed. Avoid a throttle setting which promotes rough running. NOTE.—At moderate and high altitudes it will be necessary to advance the throttle progressively to restore the falling boost and thus maintain the recommended speed. Now as the throttle is opened r.p.m, will increase and at a certain height the recommended speed will be unobtainable even at a throttle setting which gives 2,650 r.p.m. At this height the supercharger switch should be set to AUTO and the throttle then adjusted as before to maintain the recommended speed.

 

56. Fuel capacities and consumption

 

(i) Normal fuel capacity:

Top tank...................................................48 gallons

Bottom lank..............................................37 gallons

Total........................................................85 gallons

 

(ii) Long-range fuel capacities:

 

With 30 gallon " blister " drop tank.............115 gallons

With 45 gallon" blister "drop tank...............130 gallons

With 90 gallon" blister "drop tank...............175 gallons

With 170 gallon " blister " drop tank...........175 gallons

 

With rear fuselage tanks

Early aircraft.....160 gallons

Later aircraft.....151 gallons

 

NOTE.—On some aircraft these capacities are increased by 10 gallons.

 

 

(iii) Fuel consumptions: The approximate fuel consumptions (gals./hr.) are as follows:

 

Weak mixture (as obtained at +7 lb./sq.in. boost and below):

 

large.595d05100d368_FuelConsumption-WeakMix.PNG.7c91047fcb93db5d8d60c5582478c475.PNG

 

 

Rich mixture (as obtained above +7 lb./sq.in. boost):

 

large.595d050f863d9_FuelConsumption-RichMix.PNG.d85f27ef5e98bc0b26c6c7f9d04bb49a.PNG

 

 

NOTE.—The above approximate consumptions apply for all Marks of engine. Accurate figures giving the variation in consumption with height and as between low and high gear are not available.

 


Edited by DD_Fenrir
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Nice video. :thumbup:

 

Just a small nitpick you forgot to set your altimeter to 0 before take-off, so the actual cruise altitude was a bit lower than 15k feet.

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That was entertaining and educational at the same time :). My only complaints are:

a) you should turn off the engine by moving mixture lever to cutoff position, next time you fire up DCS, your virtual mechanic is going to have a serious conversation with you :D;

b) assuming the "combat" taking place over the France actually, one has to add fuel burnt on getting from the deck up to econo altitude of 15k again while heading home, unless you just decide to go back low. In either case, however, consumption would be higher than in the vid. How higher? Well, that's another thing to test, especially with more accurate tables posted above.

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Somewhat agree, I'd likely spend my 15,000ft over France and need to reclimb coming back....but that's me!

Really happy you did this OP because it actually shows me that the fuel consumption isnt bugged, but my actual flying was!

That was entertaining and educational at the same time :). My only complaints are:

a) you should turn off the engine by moving mixture lever to cutoff position, next time you fire up DCS, your virtual mechanic is going to have a serious conversation with you :D;

b) assuming the "combat" taking place over the France actually, one has to add fuel burnt on getting from the deck up to econo altitude of 15k again while heading home, unless you just decide to go back low. In either case, however, consumption would be higher than in the vid. How higher? Well, that's another thing to test, especially with more accurate tables posted above.

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That is good to know. Wonder if the AI does as well.

 

Sadly, in the other thread, Reflected reported that they are very far from "doing as well".

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  • 3 weeks later...

I have found the same. Fuel usage rates for any rpm/boost settings are anything up to twice the figure quoted in the Pilots's Notes. Even allowing for inaccurate flying and settings that is rather excessive.

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Yo-yo has commented elsewhere that the fuel flow rates are identical for the Spitfire as for the P-51D; after all they are both Merlins, n'est pas?

 

However it seems that the Packard Merlins were run slightly richer than the Rolls-Royce equivalents if DCS is correct; if this is true to life then this could be down to any number of reasons but in my mind is likely to be any or a combination (or all) of the following:

 

a) Spitfires carb jets were set leaner to glean the most from the limited fuel supply,

b) P-51 Merlins set slightly richer to provide slightly cooler charge and hence less stress on the engine for the very long range missions and hence extended engine operating periods

c) the Packard Merlins were dimensionally slightly different from Rolls-Royce as the R-R units were made to British Imperial and the US manufactured to US standard. Drawings had to be redrawn and there well could be some effect there. The tolerances apparently were also much tighter for the mass-production requirements. However - and I would estimate more importantly - the superchargers were different also; it could well be here that the crucial difference lies.

 

Whatever the actual reasons it is something that obviously requires adjusting on our DCS Spitty; however, Yo-yo is aware and I suspect we will see some fix in forthcoming update.

 

Just remember that the pilots notes also say the following:

 

NOTE.—The above approximate consumptions apply for all Marks of engine. Accurate figures giving the variation in consumption with height and as between low and high gear are not available.

 

These figures are guideline only; so don't be too generous when estimating your endurance!

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Anyone knows if fuel drop tanks are projected in future updates for the Spitfire?

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I dont like the rear fuselage tank. It changes A LOT the Spitfire handling. Or that is what the books about are saying.

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I dont like the rear fuselage tank. It changes A LOT the Spitfire handling. Or that is what the books about are saying.

 

The Mustang has the same issue: filled rear tank shifts the CG, making the plane unstable in violent maneuvering.

 

Solution is to switch fuel supply to rear tank ASAP after takeoff, and drain it first (before even the droptanks). Hopefully the fuel in the rear tank is used up before you encounter the enemy.

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The fuel load at take-off should be enough to get you to your mission target, plus enough to allow for fighting there, to get you back to base with a small reserve, just-in-case.

 

If you're getting into a fight so close to base that your rear tank still has fuel, either you got jumped by the enemy at a point, when you had no reason to expect the enemy, or you're filling the tank unnecessarily.

 

You don't need fuel in the rear tank, nor drop tanks to fly Air-Quake™, where you fly 5-10 minutes at the very most to get into a fight.

 

If you're flying a long range mission, where you need the extra fuel in the rear (and on the P-51D, drop tanks), why are you getting into a fight before that extra fuel is used up?

When you hit the wrong button on take-off

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I bet you if you take off, cross the channel, fight in France and return to England only with 85 galons ( forward fuel tanks ), you dont have time for doing almost nothing.

 

This is why we need rear tank options or a drop tank.

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I have no complaints about getting a rear and a drop tank, but there's no point in complaining about having a full rear tank wrecking the maneuverability of the Spitfire, because you should never be going into combat with a full rear tank.

When you hit the wrong button on take-off

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No if you plan your mission carefully. But sometimes you know, just someone is jumping on you by surprise.

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I bet you if you take off, cross the channel, fight in France and return to England only with 85 galons ( forward fuel tanks ), you dont have time for doing almost nothing.

 

This is why we need rear tank options or a drop tank.

 

You haven't seen the movie Dunkirk.. It IS possible.. to even shot down bombers with the engine dead :))

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  • 1 month later...

a simple flight from Beslan to Batumi heading between 230° and 270° resulted in my crashing right at the very edge of runway in Batumi while entering pattern on fumes, the fuel gauge was zero. The fuel tank was 100% loaded and cruise altitude was below 15,000 feet. Is it short ranged?

image.thumb.png.f928c1ee82b426aef38f30889185265d.png


Edited by WildBillKelsoe

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Also in DCS the Spitfire is using ONLY one of the internal tanks, the frontal tank with 85 gals. The rear tank with 29 gals cant be filled.

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Also in DCS the Spitfire is using ONLY one of the internal tanks, the frontal tank with 85 gals. The rear tank with 29 gals cant be filled.

 

Because it isn't there.

 

This tank only appeared in very late versions of the Mk.IX/XVI and is not modelled installed to the DCS model.

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The Spitfire DCS manual schematics is showing the rear tank. But if this is not modelled well, the short range is a product of the 85 galons capacity.


Edited by Esac_mirmidon

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