Spit or ME ?? Rumors revealed and busted !

[Soren]

Very interesting Sarge714, however on top of this I've got to ask; Are you an educated aerodynamicist ?

 

[Chingachgook]

Sarge,

How close is DATCOM calculations to known real world test results? If you put data in for a Cessna 152 how well do the numbers line up with the real aircrafts performance?

 

[Sarge714]

Sarge,

How close is DATCOM calculations to known real world test results? If you put data in for a Cessna 152 how well do the numbers line up with the real aircrafts performance?

Roskam has a data list for several aircraft that you can compare against. The DATCOM manual compares the quality of each computed stability derivative. Most fall in the instrument noise from flight test. A couple derivatives have larger margins. For example control force has a 30% margin. And subsonic calc's are more accurate than trans/super sonic.

The most impressive I've worked with so far was the Zero roll rate. The data in NACA 868 says is in the 55dps at 160mph. DATCOM says the A6M5 could do 109dps at 183 mph (30 lbs of stick force).

If you watch this video of Steve Hinton flying the A6M5 it supports the DATCOM roll rate.


View: https://www.youtube.com/watch?v=NUN9FqDAHEU

DATCOM has been a good tool to help separate the BS/Propaganda from reality.

 

[Chingachgook]

This may be why Hinton rated Zero just behind Bearcat among his fav warbirds when I talked with him. His Zero has no wing gunz - that may have some effect?

 

[FLYBOYJ]

Good information Sarge - but as discussed here before, what happens to that roll rate at 300+ mph?

 

[Sarge714]

Good information Sarge - but as discussed here before, what happens to that roll rate at 300+ mph?

DATCOM shows for the A6M5 about 57dps at 300mph IAS at SL. The NACA data shows about 42+ dps for the same speed at 10,000ft.

 

[denis]

the japs called the bau whispering death

 

[lesofprimus]

Its Japanese, not Japs... Please refrain from using derogatory racial slang terms here...

 

[the lancaster kicks ass]

he wouldn't have ment it to cause any offense we use the term readily and freely over here without compalaint.............

 

[lesofprimus]

Thats not true, everytime that word is used I say something... Its derogatory and demeaning and has no use here....

 

[the lancaster kicks ass]

no by over here i meant Britain.........

 

[MH434]

MANOEUVRABILITY
SPITFIRE TURNING DIAMETER = 1,760 feet. BF 109 TURNING DIAMETER = 1,500 ft.
A Spitfire pilot will tell you the Spit could turn inside the 109. A Messerschmitt pilot will tell you the 109 could turn inside the Spitfire! The truth is that both designs were capable of turning circles that would cause the pilot to "black-out" as the blood drained from the head. The pilot who could force himself to the limits without losing consciousness would emerge the victor from a turning battle, and the Spitfire pilots had supreme faith in their machine. The British aeronautical press told them that the wings came off the 109 in a dive or in tight turns, untrue but based on some early wing failures in the 109`s predecessor the Bf108.

However the 109 had a distinct advantage in manoeuvrability and turning circle at low speeds. The design of the 109, with it's leading edge slats gave a lower stalling speed. The 109 was very forgiving if stalled, with no tendency for a stall to develop into an uncontrollable spin, something that the Spitfire was prone to. Thus a Messerschmitt pilot was more at home at low speeds than his British counterpart.

Both the Spitfire and Messerschmitt became harder to control at high speeds, with greater and greater strength needed on the control column as the speed increased. However the problem was much worse in the Messerschmitt and in the high speed fights that developed in the Battle of Britain the Spitfire had the advantage. It was found that the fabric covered ailerons of the Spitfire caused the increase in force needed on the control column due to the bulging of the fabric at high speed. When metal covered ailerons were fitted the handling of the Spitfire at high speed improved greatly. Unfortunately this discovery did not take place in time to help British pilots in the summer of 1940.
.

I do not agree with this, Spits have much lower wingloading.
Most reports says spits did turn tighter.

http://www.spitfireperformance.com/spit109turn18.gif

http://www.spitfireperformance.com/spit109turn.gif

http://www.spitfireperformance.com/bank45.gif

 

[Chingachgook]

Soren never actually gave the source for this... We are not really sure where it came from.

 

[Kurfürst]

I do not agree with this, Spits have much lower wingloading.
Most reports says spits did turn tighter.

http://www.spitfireperformance.com/spit109turn18.gif

http://www.spitfireperformance.com/spit109turn.gif

http://www.spitfireperformance.com/bank45.gif

I wouldn't put much faith into those turn diagrams. They're estimates, and they can't even get the basic data such as power outputs. The Clmax are assumed, which makes the dataset as good as any guess...

The best you can do is to dig up some British source for the Spitfire, and some German sources for the 109, preferably in comparable conditions, and then see what gives.

For the 109, there are plentyful of German sources for turn.

The British estimate gives it 206 meters for the Spitfire, and 260 meters for the 109E, at 12 000 feet or 3657 meter altitude.

A Messerschmitt company document from August 1940 gives the turn time for a 360 degree sustained turn with 5-min power as 18.92 seconds, and the turn radius as 203 meters.

The Bf 109E manual gives the smallest turn radiuses as the follows :

W/o flaps, 0 meter altitude : 170 m
W. flaps, 0 meter altitude : 125 m

W/o flaps, 6000 meter altitude : 320 m
W. flaps, 6000 meter altitude : 230 m

A particularly interesting thing is the use of combat flaps. The 109E had combat flaps, and it could use them up to fairly high airspeeds. The Spitfire flaps could be only used for landing (having only 2 positions, up and down). As seen, flaps have a very marked effect on turn radius, and it could be entirely possible that the Emil can get minimally smaller turning radiuses by using them (ie. using flaps 109E: 230m/6000m vs. Spit : 206m/3600m, and altitude has marked negative effect on turn radius)


The British give something like 24-25 seconds for the 109E, so I presume they grossly overstated turn times for the aircraft, given the German figures. I presume that is because the only Bf 109E available for evalutation for the Brits was one that was originally crashlanded and captured by the French back in 1939, who later handed over the Brits, but the aircraft was in fairly rough shape even back in the French evaluations reports which mention it's poor powerplant condition.

The British estimate give ca 18.5 seconds for the Spit, which is pretty much the same as the Bf 109E turn time. The same can be said about turn radiuses, 20-30 meter differences in turn radius is good for an 'academic' debate, but it practice you can wipe your butt with such 'advantage'.

 

[Soren]

Soren never actually gave the source for this... We are not really sure where it came from.

Its from the Spitfire-community of all places buddy !

Seems even these guys agree the 109 turned tighter.

Funny isn't it ?

 

[Chingachgook]

Soren, learn to be a bit more specific. You may have found it on their website, but who did the test, where, when etc.

 

[Soren]

You and your tests