A Question about the F6F Hellcat's Performance

[BSquared18]

Hello,

I've been adding features (with one of the previous author's permission) to an F6F Hellcat in the X-Plane flight-sim program.

One thing I noticed is that two of the three people who've worked on this plane before did not configure it so that the engine would continue to run when the plane is inverted.

I find it hard to believe that the engine of a sophisticated fighter like the Hellcat would stall out if the plane was in inverted flight for more than a few seconds. Am I correct? Unless I hear otherwise, I'll change the settings to avoid having the engine quit during inverted flight.

Thanks for any insights,
Bill

 

[GregP]

Most military airplanes do not have inverted fuel and oil systems. Most are configured for no more than 5 seconds or so of inverted flight, though some will run inverted for expended periods on a header tank of fuel.

The Hellcat is no exception, it will cut out when inverted unless the pilot pumps the primer handle ... and it is good for only momentary inverted flight as far as oil goes. The reason is simple ... combat maneuvers are NOT inverted. We can take much less g-force inverted than upright and evasion takes the form of a hard pull, not a medium to small push. And it takes much more time to recover from high inverted g-forces than from high positive g-forces.

Many Italian pilots were shot down in the middle of a perfect slow roll ... they initially thought the solution to air combat was perfect aerobatics. But a slow roll is predictable and easy to target. They found out otherwise.

Aerobatics are in the combat equation only as a means to get your airplane off-plane (or off-angle) to your attacker so he can't hit you with bullets ... in WWII, that is. Today missiles make this somewhat more problematic. Negative g's are for airshows, not combat.

 

[BSquared18]

Thanks Greg. Very informative and helpful.

Bill

 

[Ivan1GFP]

I believe the Hellcat is an aircraft that has an 'aerobatic' carburetor. In CFS1, that means that it loses a bit of power when pulling negative G.
The early Spitfires and most A6M Type Zero fighters had carburetors that would not run when pulling negative G. Later Spitfires had a modification called "Miss Shilling's Orifice" or something to that effect that allowed partial power under negative G for a short time.

Good Luck on your Hellcat model. I built one for CFS quite a few years ago and I can tell you that you will find LOTS of conflicting information on the Hellcat.

GregP is still correct though: The oil system is definitely not designed for sustained inverted flight, so bad things happen if you fly inverted for more than a few seconds. We don't simulate this type of thing in CFS1, but you might in your simulator.

- Ivan.

 

[FLYBOYJ]

Inverted flight limitations should be listed on the flight manual...

 

[BSquared18]

Re: "I believe the Hellcat is an aircraft that has an 'aerobatic' carburetor."

I think that's what I saw on a list of Hellcat specs described as a "pressure carburetor," as opposed to a float carburetor.

Re: "We don't simulate this type of thing in CFS1, but you might in your simulator."

Yes, in X-Plane, the engine conks out after a few seconds if Inverted Systems isn't selected. Nice to know what the correct setting is.

Bill

 

[GregP]

Joe is correct. If you check the pilot's manual (http://aviationshoppe.com/manuals/grumman_f6f_flight_manual/f6f.html), inverted flight is only permitted to enter dives or gunnery runs. In other words, momentary inverted flight only. Same as almost all other R-2800 installations.

 

[BSquared18]

Thanks all. In the future, I'll use the two flight manuals I have. FYI, Greg, the link you provided apparently no longer is valid. As I say, no problem because I have two flight manuals.

Bill

 

[GregP]

I just clicked the link and it works for me. However, my high-end notebook that recently died sometimes had the problem of not being able to follow links that others could, so I'm not surprised about PC glitches. I probably have some windows pack that you don't have installed. I had to install a couple to get my copy of ACD Systems Canvas 15 to be able to save in jpg format, and maybe that's the difference.

Either way, most WWII fighters I an familiar with (most of the US planes at least, and several British and Japanese) have very limited inverted capabilities.

In the case of the P-51 Mustang, the horseman are a 3-man aerobatic team that make it look easy. If you Google one their performances, you'll note it is all positive g except for momentary negative to reposition.

Here's one of their performances using three Navy planes ... all with R-2800's like the F6F has.


View: https://www.youtube.com/watch?v=Gy9t8tK5yq8

It's all positive g.

 

[papashteve]

I just clicked the link and it works for me. However, my high-end notebook that recently died sometimes had the problem of not being able to follow links that others could, so I'm not surprised about PC glitches. I probably have some windows pack that you don't have installed. I had to install a couple to get my copy of ACD Systems Canvas 15 to be able to save in jpg format, and maybe that's the difference.

Either way, most WWII fighters I an familiar with (most of the US planes at least, and several British and Japanese) have very limited inverted capabilities.

In the case of the P-51 Mustang, the horseman are a 3-man aerobatic team that make it look easy. If you Google one their performances, you'll note it is all positive g except for momentary negative to reposition.

Here's one of their performances using three Navy planes ... all with R-2800's like the F6F has.


View: https://www.youtube.com/watch?v=Gy9t8tK5yq8

It's all positive g.

Hey Greg, I have a slightly off topic request for you. Is there a way to PM you? This has to do with some performance charts, and you seem to be very knowledgeable around these forums.

 

[GregP]

First, welcome to the forum!

The PM feature is up at the top left in the menu choice called "Private Messages." I'm "GregP." When you get a PM, the menu choice called "Notifications" will alert you.

I'd be happy to talk with you and there are plenty of guys in here who are knowledgeable including the moderators. These guys come for all over the world and are all WWII aviation nuts, which is a good thing. We sometimes disagree on points, but not much on the real world aircraft. It's mostly about what would happen if something changed. I call these "what ifs."

To get a good solid cross-section response, possibly including some dissenting but still interesting opinions, consider posting a question in the forum ... but I'd also be glad to communicate via PM if you like.

Again, welcome.

Best regards, - Greg