Author Topic: D9 compresses to early. Test and source given... (Read 988 times)

Naudet · « **Reply #15 on:** March 27, 2002, 04:19:12 PM »

FLS you did the test and reached 450 mph IAS with moderate buffeting?

Thats interesting, cause in both dives i made the plane nearly tore apart at 400mph IAS @20k.

Will have to do some more testing on that.

What was you fuel loadout? It should not have influence, but who knows.

Edit: I have redone the test, again, heavy shaking when getting over 400 mph IAS @20k. I level out, at 19K and plane calmed dowe when speed falls under 400 IAS.

I also filmed it, but to my surpise, the film doesnt show any buffeting or shaking.

How can that be, those films not a 1 to 1 copy of the flight?

Wilbus · « **Reply #16 on:** March 27, 2002, 04:42:31 PM »

Shaking and such, blackouts etc don't show up on film naudet.

Wotan · « **Reply #17 on:** March 27, 2002, 04:45:43 PM »

I did the same just now Naudet at of near 400 ias (just under 20k) I was shakin violently appear to be close to ripping apart.....

Good work Naudet..........

doh my film dont show it either

Glasses · « **Reply #18 on:** March 27, 2002, 05:23:43 PM »

Well we have proof about it even karnak supports it what now?

should they fix this little thing and give the hunstang some teeth or will it be left as is.....<190F8>

nuff said

hazed- · « **Reply #19 on:** March 27, 2002, 05:40:52 PM »

gripen · « **Reply #20 on:** March 27, 2002, 05:49:36 PM »

I have seen documentation which states mach 0,76 as critical mach number of the Fw 190. There should be not much difference between the A and D (same wing).

gripen

wells · « **Reply #21 on:** March 27, 2002, 06:22:37 PM »

Indicated speed is not corrected for compressibility. You can take a good 15 knots off of that figure to get the 'real' speed. Pyro has said that the airspeed indicator in AH reads CAS (calibrated for installation errors). It might even be EAS (corrected for compressibility).

http://142.26.194.131/aerodynamics1/Basics/Compressibility_Chart.html

funkedup · « **Reply #22 on:** March 27, 2002, 08:55:54 PM »

0.76 Mach at 20,000 feet is about 395 mph IAS.
Which means that Naudet's flight test finding is consistent with the published critical mach number obtained by Gripen. And the points brought up by FLS and Wells explain the discrepancy from Wagner's account of Tank's test flight. I don't see how Hitech can view this as anything but a non-issue.

MANDOBLE · « **Reply #23 on:** March 27, 2002, 10:30:24 PM »

Gripen, do you have references to that documentation stating 0.76 as critical mach?

btw, any info about typh critical mach?

gripen · « **Reply #24 on:** March 27, 2002, 11:22:58 PM »

Mandoble,
That claim is from a collection of German notes on Flight characteristics of Fw 190 and Bf 109, available from the PRO as DSIR 23/14226. Data sheet of the Fw 190 gives following IAS limits:
9000m 500km/h
7000 600
5000 700
3000 800
2000 850

Critical mach number of the Typhoon should be around mach 0,64.

gripen

Naudet · « **Reply #25 on:** March 28, 2002, 01:25:29 AM »

gripen, i got the info critical mach number for the FW190 was 0.8, can you give the source were you got the 0.76 from?

and the numbers you posted from the PRO report, those limits were marked on the airspeed indicator of a ditched FW190D9 from 2nd Jan 1945.

There was no test done as far as i know from the RAE on FW190 divespeeds.

So it seems Tanks dive is too me the only know test yet.

And about the correction, if you can take a 15 knots of (around 18mph right?) the AH D9 still compresses about 15 mph to early.

As i said the difference i found was 35-40 mph, substrat 20 from it and you still have a differnece left of 15-20.

But i try to to a test on gripens numbers. As far as i can remember the AH would is be capable of 850km/h (528mph) @2km (6557 feet).

gripen · « **Reply #26 on:** March 28, 2002, 02:53:15 AM »

Naudet,
The source is mentioned above, just go to:

http://catalogue.pro.gov.uk/

And you can find it using reference number mentioned above. And it is not a RAE report but a collection of German notes. Also mentioned dive IAS limits are not from RAE but from original datasheet of the D9 so these should same as in the indicator.

gripen

HoHun · « **Reply #27 on:** March 28, 2002, 03:04:54 AM »

Hi Gripen,

working with the compression correction chart Wells linked, the Fw 190D-9 placard works out to the following Mach numbers:

9000m 500km/h Mach 0.71
7000 600 0.74
5000 700 0.76
3000 800 0.77
2000 850 0.77

Of course, placard values tend to be conservative and are not only selected for the Mach number, but also for the desired engine revolutions. The Fw 190D-9 numbers look quite ambitious, though, so I speculate the impact of the latter wasn't decisive.

>Critical mach number of the Typhoon should be around mach 0,64.

That's interesting, we recently discussed it but had no numbers. I guess the Mach number is from PRO records as well?

Regards,

Henning (HoHun)

FLS · « **Reply #28 on:** March 28, 2002, 06:18:59 AM »

Note that the compression correction chart is for CAS not IAS. The
IAS position error is greatest at minimum and maximum airspeeds. You have to correct Naudet's posted IAS speeds to CAS before adding the compression correction.

--)-FLS----
Musketeers

gripen · « **Reply #29 on:** March 28, 2002, 07:10:11 AM »

HoHun,
Mach number 0,64 for the Typhoon is from "RAF fighters part2" by Green and Swanborough (same number is also mentioned in couple articles from the 40s like Aeroplane, March 1945). It is not real tactical limit but just a speed where the wing entered the compressebility region, tactical limit should be somewhat higher. In the case of the Tempest similar number was mach 0,73 but the tactical limit was mach 0,8.

gripen