Spitfire mk.V - Negative G / Outside loop.

[69th_Mobile_BBQ]

I don't fly the Spitfires very much but, I decided to take a mk. V for a solo flight in QMB.   

 

I don't know if this is supposed to be a model with the inverted fuel flow issue "corrected"   (Sorry my lack of history knowledge on the subject)

 

To test whether or not the fuel system was prone to choking while inverted I turned it over on it's back.  There was no immediate choke-out so I assumed it is a model with the corrected fuel system.  

On a whim, I decided to attempt an outside loop, basically turning inverted and pushing the stick forward as far as the plane would handle and to near-red out.  I started the maneuver around 280mph with 2650rpm and 7lbs boost.  There wasn't even a hint of engine choke well the pilot was 90% redded-out and that's a pretty fair amount of neg-G.     

All I'll say is I was quite surprised to see the plane was quite able to go  over the top and come to level 180 degrees the opposite direction within mere seconds.  

Considering that a normal positive G loop would probably take longer due to pilot physiology modeling, it doesn't seem to  me that this should be a thing the plane should be capable of.   I don't even think 109 early model pilots online could pull this without losing control of the plane and considering how many of them really push what neg-G ufo-ing can be done to shake a pursuer, that's saying something.  I have yet to try it though.  

 

To reproduce what I did:  Fly at max continuous setting > 2650rpm, 7lbs boost, water radiator 20%  

Fly level at about 2,500 feet until ~280mph is reached.  Roll inverted and push the stick forward. Try to keep the pilot at near full red-out until the plane comes to a level position facing 180 degrees from your starting course. Note how long it takes to finish the maneuver.  

[JG7_X-Man]

37 minutes ago, 69th_Mobile_BBQ said:

I don't fly the Spitfires very much but, I decided to take a mk. V for a solo flight in QMB.   

 

I don't know if this is supposed to be a model with the inverted fuel flow issue "corrected"   (Sorry my lack of history knowledge on the subject)

 

To test whether or not the fuel system was prone to choking while inverted I turned it over on it's back.  There was no immediate choke-out so I assumed it is a model with the corrected fuel system.  

On a whim, I decided to attempt an outside loop, basically turning inverted and pushing the stick forward as far as the plane would handle and to near-red out.  I started the maneuver around 280mph with 2650rpm and 7lbs boost.  There wasn't even a hint of engine choke well the pilot was 90% redded-out and that's a pretty fair amount of neg-G.     

All I'll say is I was quite surprised to see the plane was quite able to go  over the top and come to level 180 degrees the opposite direction within mere seconds.  

Considering that a normal positive G loop would probably take longer due to pilot physiology modeling, it doesn't seem to  me that this should be a thing the plane should be capable of.   I don't even think 109 early model pilots online could pull this without losing control of the plane and considering how many of them really push what neg-G ufo-ing can be done to shake a pursuer, that's saying something.  I have yet to try it though.  

 

To reproduce what I did:  Fly at max continuous setting > 2650rpm, 7lbs boost, water radiator 20%  

Fly level at about 2,500 feet until ~280mph is reached.  Roll inverted and push the stick forward. Try to keep the pilot at near full red-out until the plane comes to a level position facing 180 degrees from your starting course. Note how long it takes to finish the maneuver.  

 

Dude! What are you doing! You will get banished from the BLUE side for speaking such blasphemy! 

Seriously though - it was fixed while the British were still in North Africa, so that would be around early to mid '41. I am also 100% sure it was a female engineer that came up with the stop gap.

 

The Brass Ring

 

Found it!

Edited August 5, 2020 by JG7_X-Man

[69th_Mobile_BBQ]

14 minutes ago, JG7_X-Man said:

 

Dude! What are you doing! You will get banished from the BLUE side for speaking such blasphemy! 

Seriously though - it was fixed while the British were still in North Africa, so that would be around early to mid '42. I am also 100% sure it was a female engineer that came up with the stop gap.

 

The Brass Ring

 

Looking it up now.

 

I was aware of the fuel system correction.  I just didn't know how early it was implemented.  

 

I thought that maybe Blue would appreciate a guy who flies mostly Red saying a particular Allied plane seems to be "off" to me.  I mean a near-red-out 1/2 outside loop at that speed completed in  ~10 seconds with not much required stick and rudder coordination?  We're probably getting into Bf-110e territory here! ? (I joke)  I'll test that too though.   

 

Some further testing:   

 

Yak-1.69:   Much slower to complete maneuver.  Engine temporarily chokes once complete but doesn't cut.  

Me-109 E7:  Much slower to complete maneuver - requires much more stick and rudder coordination.  AtA (1.2) stays the same but, engine sound seems to be somewhat fuel-starved for a few seconds.  

FW-190 A3:  Doesn't like it at all.  Couldn't coordinate the plane well enough to get past the first 45 degrees nose-up.  Red-out also seems to onset earlier than the other 2 tested planes.

[JG13_opcode]

Forgetting the aerodynamics for a moment, can anyone with hands-on experience comment on whether or not an outside/negative-G loop is even possible in terms of pilot physiology?  Paging @busdriver

 

Intuition tells me you'd red-out completely and this shouldn't be possible.

[unreasonable]

On 8/5/2020 at 8:02 AM, JG7_X-Man said:

 

Dude! What are you doing! You will get banished from the BLUE side for speaking such blasphemy! 

Seriously though - it was fixed while the British were still in North Africa, so that would be around early to mid '41. I am also 100% sure it was a female engineer that came up with the stop gap.

 

The Brass Ring

 

Found it!

 

Installation of Miss Shilling's orifice completed by March 1941 according to wiki, but this would have only worked for very short periods, as in the initial stage of a bunt. Pressure carburettors that work inverted had to wait until 1943 so the Vb would probably not have had these.  (?)

 

Whether you have pressure carburettors or not, the additional problem with sustained negative G flight is that most fuel pumps and tanks work on the assumption of positive G. There was a Bf109 that crashed a few years ago after the engine cut after reverting to normal flight after ten seconds of inverted flight, due to fuel starvation. When upside down the fuel in the tank did not reach the exit port so the fuel line filled with air. Accident report is somewhere online. 

 

When I tested the Spitfires IX (ie with pressure carburettors) in level inverted flight the rpms started to cut after 15 secs.  Not sure how or why this varies between planes either in RL or in the game, but the mechanism is certainly there.

[357th_KW]

Oil starvation would likely be a big problem as well.

[41Sqn_Skipper]

 

[69th_Mobile_BBQ]

On 8/5/2020 at 10:10 PM, JG13_opcode said:

Forgetting the aerodynamics for a moment, can anyone with hands-on experience comment on whether or not an outside/negative-G loop is even possible in terms of pilot physiology?  Paging @busdriver

 

Intuition tells me you'd red-out completely and this shouldn't be possible.

 

Sorry for the late response.  Busdriver hates my guts, so most likely he won't be responding.  Perhaps we can get a real pilot, not a fuel truck attendant, to answer.    

Edited September 3, 2020 by 69th_Mobile_BBQ

[JtD]

Yes, it is possible. You can see them at airshows or if that's not possible, on youtube.

[Cpt_Siddy]

16 hours ago, JtD said:

Yes, it is possible. You can see them at airshows or if that's not possible, on youtube.

 

 

With or without modern fuel and oil systems installed? 

[JtD]

I don't think pilot physiology is effected by fuel and oil systems.

Edited September 4, 2020 by JtD

[Cpt_Siddy]

No, but oil and fuel starvation is.