Today I learned... (inverted flight)

[Hazardpro]

10 hours ago, Rainmaker said:

Fuel/oil…it can all be problematic. In the state its in, you have a chance for recovery vs bearing seizing for example, which could be catastrophic.  Same as over-g modeling (stressing the wing tip vs flat ripping the wing off).  There was some actual forethought put into what could be considered ‘fair’ from a gameplay perspective when limits get exceeded.   

Right, was just responding to all the earlier replies that were talking about the oil system. I'm not as familiar with the F100 specifically but oil starvation would present very differently than what's in the game. I think that level of detail is probably beyond what's necessary in DCS anyways. It's not full fidelity engine simulator. 

[Theodore42]

11 hours ago, GGTharos said:

-gz are not useful.  They will destroy your +gz tolerance as well ... keep the gz positive.

Wrong,

-gz when following terrain is called bunting.

-gz is useful for modifying geometry to enter into a target's turn circle when you don't have time to flip inverted, correct, and then flip back (or just don't want to show the target your cold side).

-gz is useful for avoiding a collision so you don't lose sight of what you're trying to miss.

isn't there a really famous example from WWII of the tactical validity of -gz? 

If you discount the entire regime of -gz then you're going to be making some pretty unnecessary mistakes.

[Rainmaker]

6 hours ago, Hazardpro said:

Right, was just responding to all the earlier replies that were talking about the oil system. I'm not as familiar with the F100 specifically but oil starvation would present very differently than what's in the game. I think that level of detail is probably beyond what's necessary in DCS anyways. It's not full fidelity engine simulator. 

Yup, my post wasn't directed at you per say, just quoted and added context of how it got to where it got.

[Holbeach]

On 8/23/2023 at 10:02 PM, sirrah said:

Ah that makes sense. Thanks for clarifying  

I was only thinking about fuel (and at least in the Viper with its siphoning system, inverted flight shouldn't be an issue), but I didn't consider engine oil feed limitations.

In my defense, I was an airframe bloke back in my RNLAF days. Apart from removal and installation we didn't do anything with the engines

 

@Swift.; I know, the human in the jet, as usual, is the limiting factor . I was just a bit surprised about the mechanical aspect.

 

So, when flying inverted for over 10sec in negative G, the engines are cut off automatically as a safety measure, to prevent them from running dry (oil wise) and overheating the bearings? Did I understand that correctly?

Or will the bearings already have run dry by then, resulting in major damage/engine fail?

 

The F16 also has 10 sec -G limitation, but it doesn't have the same zero G flight prohibition, as do the F15 and F18.

No, the engine won't go bang at 10 sec or shut down, just don't fly in neg G.

F15/F18 are prohibited 0G manoeuvres except transient.

Flamout after 14 sec can only be fuel, (a handy game limitation).

My only question is. Why are people so disappointed that they can't fly upside down, ad infinitum?

 

..

[sirrah]

6 minutes ago, Holbeach said:

My only question is. Why are people so disappointed that they can't fly upside down, ad infinitum?

Which people are disappointed? I don't see anyone complaining about anything...

Most, if not all of us, know that negative G isn't really good for anything (especially not for human beings).

We, or I at least, were just wondering what technical aspect causes the flameout. That has been answered (several times now)

[Hazardpro]

In case anyone is curious there are engines out there newer than the F100 with auxillary oil systems designed to maintain some OP in -g regimes. The ones I know of are actually commercial engines so it's a concern even for airliners which obviously aren't meant to be perfoming in airshows but could still end up in flight upsets for other reasons.

[GGTharos]

11 hours ago, Theodore42 said:

isn't there a really famous example from WWII of the tactical validity of -gz? 

If you discount the entire regime of -gz then you're going to be making some pretty unnecessary mistakes.

You can believe whatever you want to believe.

[Nealius]

20 hours ago, Theodore42 said:

isn't there a really famous example from WWII of the tactical validity of -gz?

That old Spit vs. 109 story? The premise I always heard on that was the 109 can bunt the nose and dive away while the Spit couldn't. They seem to have forgotten how to roll inverted and pull positive G to dive.

[jaylw314]

17 hours ago, Nealius said:

That old Spit vs. 109 story? The premise I always heard on that was the 109 can bunt the nose and dive away while the Spit couldn't. They seem to have forgotten how to roll inverted and pull positive G to dive.

IIRC, that had more to do with the float carburetor in the Spit (immediate fuel starvation) than the typical fuel tank stuff people are talking about here.

[jaylw314]

On 6/26/2023 at 4:17 AM, Lace said:

The Mud Hen doesn't like sustained inverted flight.  Around 10 seconds to double engine flameout at 300ft made for an interesting end to that particular sortie.  I guess that's one reason the Thunderbirds use Vipers.

FWIW, I recall the Blue Angels need to modify the legacy Hornet's fuel system for sustained inverted flight

Edit: Apparently the Super Hornets also needed similar modifications

[72westy]

On 8/26/2023 at 3:42 PM, jaylw314 said:

FWIW, I recall the Blue Angels need to modify the legacy Hornet's fuel system for sustained inverted flight

Edit: Apparently the Super Hornets also needed similar modifications

Correct. The demonstration aircraft are stripped down & modified to fly sustained maneuvers. Spent 10 years working as an AD-1 in the Navy (1986-1996).