Wingload - tables for AH planes

[HoHun]

Hi Gripen,

>More relevant comparison might be clmax for say 3 g or  complete v/g flight envelope based on real world tests just like RAE did with Spitfire I and Bf 109E.

I guess you're referring to the same graph I was quoting the Clmax figures from? If you have any background information on it, it would be appreciated.

Regards,

Henning (HoHun)

[gripen]

HoHun,
I have the whole RAE report (RM No. 2361). Actually this is a version published by the Aeronatical Council after war; well printed and clean if compared to original (available from British library as well as many technical universities have this series). The flight envelope of the Spitfire is based fully on flight tests. In the case of the Bf 109 the flight envelope is partially calculated (stall speeds are tested). Stall tests of the Bf 109 gives Cl 1,4 with slots power off, slots came out at Cl 0,865 (these are tested values). Power on clean 1g Clmax is calculated as 1,95 (I quess you have same graph). The Plane tested was AE479 (captured in France), DG200 was captured after release of this report.

gripen

[wastel1]

weight of an early, non mw50 G6 is 6922lbs (3140kg)
and not 7150lbs


wastel

[HoHun]

Hi Gripen,

>I have the whole RAE report (RM No. 2361).

Do you happen to have it in electronic form? I'd just love to have a look at that report :-)

>The flight envelope of the Spitfire is based fully on flight tests.

That's interesting as it gives different Clmax values than the NACA report. (The impact of that difference is not as big as one would imagine since lift increases with velocity squared).

>Stall tests of the Bf 109 gives Cl 1,4 with slots power off, slots came out at Cl 0,865 (these are tested values). Power on clean 1g Clmax is calculated as 1,95 (I quess you have same graph).

I've got the graphs, and van Ishoven indeed quotes the same 1.4, which is rounded from the 1.38 I calculated from the test figures.

The 1 g clean Clmax would include extended slats, wouldn't it?

It seems NACA report "Calculated and Measured Turning Performance of a Navy F2A-3 Airplane as Affected by the Use of Flaps" applies the same method to the Brewster Buffalo.

Here's a comparison:

F2A-3 no flaps 13000 ft 900 HP: 25 s/360°
Spitfire (RAE test) 12000 ft: 19 s/360°
Me 109 (RAE test) 12000 ft: 25.5 s/360°

I was confused about which variant of Spitfire the RAE used for comparison, so I superimposed the "angle of climb" curve of Spitfire N.3171, a Mk.I with a Merlin III running at 6 1/4 lbs/sqin to the RAE graph:

Spitfire N.3171: 21.5 s/360°

(Weight of N.3171 was 6050 lbs, so I assume it didn't have pilot armour installed.)

Is it correct that Spitfire IA K.9791 was used by the RAE for the comparison? I'm not sure why it performs so much better than N.3171.

I don't think the Me 109E really had 1200 HP available, by the way. I wonder if that affected the calculations?

Regards,

Henning (HoHun)

[Angus]

CL is a figure for a certain square right?
So to produce total lift it is a function involving both CL and Wing area?

[GScholz]

Yes, CL is a function that describes how efficient the wing is at producing lift not linked to wing area. A huge wing with low CL will still produce more lift than a tiny wing with high CL.

[HoHun]

Hi Angus,

>So to produce total lift it is a function involving both CL and Wing area?

To be exact, total lift is proportional to the product of lift coefficient and wing area.

Lmax = Clmax * 1/2 * rho * v^2 * A

Lmax = maximum lift
Clmax = maximum lift coefficient
rho = air density
v = true air speed
A = wing area

Regards,

Henning (HoHun)

[gripen]

HoHun,
I just have paper copies from BL.

Naca did not test Spitfire at similar power settings as RAE (not just MAP but also rpm) and tested model is also different  (a bit heavier). Otherwise I don't see much difference between Clmax values on NACA and RAE tests (clean power on values). IMHO they support each other very well given the differences on power settings (this is true also on aileron tests of Spitfire). Overall RAE and NACA tested planes with very similar methods and there were really lot of know how transit between these organisations (NACA F2A report actually claims RAE references and same references are also claimed in RAE Bf 109 report). In fact methods used by DVL appear to be also suprisingly similar.

RAE Clmax values of Bf 109 are with slats open but as noted they also measured at which speed (or Cl value) they came out.

I don't know which particular Spitfire was used for turn tests, report just claims that Stall boundary has been measured in flight.  Which power setting was used on Spitfire N.3171?

gripen

[Angus]

You are great. Much information around much quicker than reading through piles of books.
The (lift) induced drag will then presumably always touch the subject of lift, right? The more total lift, the more lift-induced drag?
Really, lift induced drag is there as a function of TOTAL lift isn't it?
Just wondering..again....about something particular,,,will explain later

[HoHun]

Hi Gripen,

>Naca did not test Spitfire at similar power settings as RAE (not just MAP but also rpm) and tested model is also different  (a bit heavier).

Actually, aircraft weight doesn't influence Clmax as this is characteristic for the wing.

And in a turn, the difference between cruise and combat power would be hardly noticable:

"This value of maximum lift coefficient is closer to that reached from stalls in straight flight with power off than the value reached with power on because the slipstream effects in high-speed turns are relatively small."

(From the NACA report.)

>Which power setting was used on Spitfire N.3171?

6.25 lbs/sqin, compared to 6.5 lbs/sqin for the Spitfire on the graph.

Regards,

Henning (HoHun)

[Tilt]

I dont really understand these............

wind tunnel tests with la7 at various AoA..the photos dont show a prop.............



Does this show a Cl of approx 1.4?

I have other similar graphs showing various straight line functions and one other inverse curved line graph.

[HoHun]

Hi Tilt,

>wind tunnel tests with la7 at various AoA..the photos dont show a prop.............

Great scan! I wish we had data like that on any other plane! :-)

The pair of "rounded" lines show lift polars in the standard way (Cl vs. Cd, upper scale on horizontal axis).

The pair of "straight" lines show Cl vs. AoA (lower scale on horizontal axis).

I don't immediately recognize the two short parabolic graphs, though.

What does the Russian text say? :-)

Regards,

Henning (HoHun)

[gripen]

HoHun,
You are correct that weight does not affect Clmax but NACA tested Spitfire V and RAE tested Spitfire I.

Only comparable Clmax values in RAE and NACA tests are 1 g power on values ie not high speed turning. NACA claims Clmax 1,63 and 1,68 on 3,75lbs/2650rpm and 1,64 on 7lbs/2850rpm. RAE claims Clmax 1,87 on 6,5lbs/3000rpm. I don't know what is the real difference between engine output because engine models are different (Merlin III had lower SC gear ratio), I quess something like 100-150hp.

gripen

[hitech]

Looks like induced drag?

HiTech

[Tilt]

The ac in question is the one and only La7 TK. which is a std La7 with 3rd stage super charger added.

I have 12 pages of text full of formulae I dont understand in Russian to accompany several pages of photographs and graphs similar to the one above. (graphs are straight [horizontal] line graphs referings to Cx and V and a negative sloped graph refering to m2 and angle)

The pictures show three shots for each AoA each with the exhaust vents at different apertures.

I believe this work was done on the 9/IX/44.

If its considered important I will scan and zip it to a site where it can be accessed.


Edit.

I assume the pairs of lines are with and without slats extended. (CL only really changes between them at higher AoA)..........

The Russian text idnetifies it propoerly on the graph if someone can translate.......

Could the other short curve be with flaps fully lowered?