Why still no dive acceleration difference?

[BlackBerry]

Originally Posted by RegRag1977

Since this interesting topic is about propeller types and dive efficiency, i just wanted to ask if, for instance, the fact that the Spit switched from three to four blades prop did allow it to improve its dive performance and to reach better dive speeds than the 109 which kept its 3 blades prop through the entire war period, as we know. Since both designs are very similar in the concept i'm sure the use of a different propeller would show in terms of DIVE performance?

I would like to see the relative dive performance of the aircraft between 109, Spit MkV and later MkIX. I think it could help answering the question we are asking ourselves? If someone knows about this it would be very nice!

PS My prejudice so far is that the 109 always dove better than the Spit (three or four blades propeller) Please correct me if i'm wrong

Good post. There is dive acceleration between spit IX/XIV and bf109G6as(m).
http://www.wwiiaircraftperformance.org/sl-wade.html

http://www.wwiiaircraftperformance.org/wade-dive.jpg

Notice that the boost pressure of bf109G is 1.75ata, so that's bf109G equipped with MW50.

The source says the dive acceleration (looks like 45 degree)of spitfire IX and BF109G6as is roughly same, but it also points outs that spitfire IX was outdived by bf109g6as INITIALLY.

It's very interesting to find initial dive advantage of German aircraft for many times . History is telling us some clue that we should pay enough attention to.

My comprehension of this report is:

When both spitfireIX and BF109G6as fly side by side with same speed/altitude, and begin to dive from low-medium speed, bf109g6as will outdive spitfireIX. The reasons are obvious,:

1) bf109 has better engine thrust/weight rario because same engine output/prop efficiency at low-medium speed but 109 is lighter.

2)bf109 has smaller wing area, so less air drag than spit.

It was widely accepted that bf109 could outdive spitfire INITIALLY among RAF pilots during WWII.

However, as speed building up, spitfire IX begin to catch up with bf109! Roughly near max allowable, spitfire IX could become "side by side" again with bf109. therefore, both dive accelerations are roughly same. And spitfire XIV will slightly ahead of bf109g6as in the end of high speed dive, although still be outdived INITIALLY.

There is also indirect comparation:
http://www.hawkertempest.se/TacticalTrials.htm

When comparing tempestmkv and spitfire XIV, it says:

Dive
The Tempest gains on the Spitfire XIV

Comparing with bf109G

Dive
Initial acceleration of the Tempest is not marked, but a prolonged dive brings the Tempest well ahead.

So we can also include that bf109G outdive spitfire XIV initially, but spitfireXIV could slightly outdive 109G at high speed.

Why 4-blade propeller spitfires dives quite fast at high speed? More weight than bf109? Perhaps.More propeller efficiency at high speed? Perhaps.