Author Topic: 190D9 elevator authority (Read 528 times)

Wilbus · « **Reply #30 on:** March 06, 2002, 12:18:42 PM »

Find it odd that the Spit would have a higher critical mach then the 262, specially since the 262 could go supersonic, and prop plane can't.

Seeker · « **Reply #31 on:** March 06, 2002, 12:34:39 PM »

Because all critical mach tells you is at what speed compression sets in, it says nothing of how much the airframe is compressed, or how it handles the effects.

The 262 (if I've got me numbers right) did (or would) compress at a lower speed than the Spit, but could puch through it; perhaps to supersonic flight.

Compression doesn't *have* to mean a controls locked death dive. It may be so have so mild and fleeting effect as to go unnoticed, as in modern jets. It's no more than really wierd and disturbed airflow; it's how well the design handles that that's the key.

Naudet · « **Reply #32 on:** March 06, 2002, 05:10:07 PM »

OK did some investigations and asking a couple of people that really have a huge database on the FW190, i found the following out.

Kurt Tank wrote a flight reported, in which he performed some dives, no real maximum dive speed tests.

He flew 435 IAS @19685feet

that would be 606 TAS at that alt

and if you calculate if for 10K it would be 505 mph IAS.

Tank noticed that at those speeds no buffeting accured.

Cause speed of sound increases the lower you get, i wonder why the AH D9 compresses at around 480 mph IAS when below 10k in AH.

MANDOBLE · « **Reply #33 on:** March 07, 2002, 06:23:41 AM »

Naudet, can u present any book reference, link or scanned document about that Tank test? If u can present any proof, HTC crew will be able to fix a supposed deviation of 25mph or more before buffeting, and probably critical mach also, as well as control authority degradation.

Naudet · « **Reply #34 on:** March 07, 2002, 05:15:13 PM »

I have this information from Bryan Bury, the guy who did the real great D9 page at http://jagdhund.homestead.com/files/Dora.htm

have you done any test using D9 at 19685 feet?

my calculate IAS of 505 @10k matches about the behaviour of the A8 in a dive.

MANDOBLE · « **Reply #35 on:** March 07, 2002, 06:24:18 PM »

Excelent link, but please, edit it cause the text is ok while the link is wrong.

It has very interesting info about the boost system endurance. New topic OTW

funkedup · « **Reply #36 on:** March 07, 2002, 06:42:49 PM »

What determines onset of compressibility (compression is not an aviation term) is Mach number. This is the ratio of TAS to the local speed of sound. IAS has nothing to do with it. Every plane has a critical Mach where shockwaves start to form, and this is when compressibility effect start.

IAS gives an indication of dynamic pressure, which is what puts stress on the airframe. Every airplane has a maximum IAS where either overstress will occur or some sort of buffet/flutter/aeroelasticity will happen.

Depending on the aircraft and altitude, sometimes Mach number is the limit, sometimes IAS is the limit.

Naudet · « **Reply #37 on:** March 08, 2002, 04:47:52 AM »

funkeup, were can i find a table were mach number and actual speed of sound in mph or km/h is shown?

I searched one but couldnt find one.

Or can someone give me the the factor what 1 knot is in mph or km/h.
Than i could extract the speeds out of seekers chart.

Furious · « **Reply #38 on:** March 08, 2002, 10:44:00 AM »

1 nautical mile = 1.151 miles = 1.852 Km

A great converter:
http://pointa.autodesk.com/local/enu/portal/converter/ConverterLeaf.jsp

F.

Furious · « **Reply #39 on:** March 08, 2002, 11:20:59 AM »

Also, a very nice site on Mach Numbers:

http://ewhdbks.mugu.navy.mil/mach-as.htm

It is a military site and slow as molasses, but worth the wait.

F.

MANDOBLE · « **Reply #40 on:** March 08, 2002, 11:47:06 AM »

.mil

Furious · « **Reply #41 on:** March 08, 2002, 12:41:37 PM »

ok, try this.

Furious · « **Reply #42 on:** March 08, 2002, 12:42:18 PM »

and this.