F15E engines stall even faster than F14A

[lax22]

Was surprised to find out that when I’m doing a 90 degree climb in the F15E, both engines go out pretty much every time once I get to the top and I have to restart them in the air.

When doing the same maneuver in the F14A, I get some loud bangs from the engines to let me know they’re not happy but they don’t actually go out.

I thought that the engines in the Eagle are not as touchy as the ones in the Tomcat…

 

[Rainmaker]

Are we talking about high altitudes here or what?  

[lax22]

37 minutes ago, Rainmaker said:

Are we talking about high altitudes here or what?  

around 45k 

[AndyJWest]

When you say 'get to the top', are you holding it 90 degrees up until the airspeed drops to next to nothing? Do that, and its going to be anyone's guess what happens, given that g can go pretty much to zero, and AoA to anything at all? Neither is conducive to keeping an engine running while gravity takes over and gives the aerodynamics something to work with...

[VFA41_Lion]

Eagle goes up to at least 55,000 feet. Different airplanes built differently behave differently... is that such a shock?

[lax22]

5 hours ago, VFA41_Lion said:

Eagle goes up to at least 55,000 feet. Different airplanes built differently behave differently... is that such a shock?

Goes up to at least 55k feet? What does that even mean?

How high the plane goes when you do a 90 degree climb depends on the weight of the plane and at what speed and altitude you start the climb. The statement about it going to at least 55k ft is therefore plain wrong.

And no, it's not a shock that planes behave differently. I was just surprised that I had to start the F15 engines in the air within a couple of days about as often as I did that with the F14 engines in a couple of years.

[Despayre]

11 hours ago, lax22 said:

The statement about it going to at least 55k ft is therefore plain wrong.

 

This statement is untrue.

Not sure what you're trying to suggest here, but if you can't get the Eagle up to 55,000 for some reason, you're doing something wrong, it *definitely* can get there.

[lax22]

10 minutes ago, Despayre said:

This statement is untrue.

Not sure what you're trying to suggest here, but if you can't get the Eagle up to 55,000 for some reason, you're doing something wrong, it *definitely* can get there.

Did you even read the original post?

The question is not what the max ceiling for the F15 is but what the behavior during a 90 degree climb is once you run out of energy (spoiler alert: the engines will stall)

[Despayre]

1 hour ago, lax22 said:

Did you even read the original post?

The question is not what the max ceiling for the F15 is but what the behavior during a 90 degree climb is once you run out of energy (spoiler alert: the engines will stall)

Ya, I read it...

You: "Dr, it hurts when I do this..."

Dr: "Don't do that."

 

What is your valid use-case for having to do this IRL? We're not test pilots.

 

[lax22]

1 hour ago, Despayre said:

Ya, I read it...

You: "Dr, it hurts when I do this..."

Dr: "Don't do that."

 

What is your valid use-case for having to do this IRL? We're not test pilots.

 

So you read it but didn’t understand it, but that’s ok.

At least some F14 instructors showed that exact maneuver to some of their student pilots (see F14 documentary “Tomcat Tales”)

And no, we’re not test pilots, we are people playing a video game…

 

 

[Despayre]

57 minutes ago, lax22 said:

So you read it but didn’t understand it, but that’s ok.

At least some F14 instructors showed that exact maneuver to some of their student pilots (see F14 documentary “Tomcat Tales”)

And no, we’re not test pilots, we are people playing a video game…

 

 

So you don't have a use-case, just wanna complain about something, but that's ok. 

Got it.

[lax22]

2 hours ago, Despayre said:

So you don't have a use-case, just wanna complain about something, but that's ok. 

Got it.

I was not complaining, I just noticed something that surprised me and was wondering if other people also noticed it.

I don't know however why you are still responding to this thread.

First you didn't understand the topic and then you made abundantly clear that you don't have anything useful to contribute...

[Despayre]

3 hours ago, lax22 said:

I was not complaining, I just noticed something that surprised me and was wondering if other people also noticed it.

I don't know however why you are still responding to this thread.

First you didn't understand the topic and then you made abundantly clear that you don't have anything useful to contribute...

Finally, we agree, you weren't complaining. You were whining.

And wh? Because I just found your lack of ability to read and understand English, and your assumption that the problem was at my end, amusing. I don't know why you keep responding either, but I'm still amused, so, carry on with your childlike insults if it makes you feel better somehow.  

[dorianR666]

9 hours ago, Despayre said:

What is your valid use-case for having to do this IRL?

why should there have to be a usecase for this maneuver? this is a sim. if something behaves (supposedly, i cant judge it) unrealistically, then its a bug.

it doesnt matter that the activity is unusual IRL.

Edited June 28, 2023 by dorianR666

[AndyJWest]

F-15 intentional tailslide. Doesn't go quite as planned. Not that planning makes a lot of difference when you do this.

Given that (upright) intentional spins are prohibited in the F-15E, along with AoA over 30 units,  and negative g for more than 10s, I'd be surprised if intentional tailslides were permitted other than for test flights. As speed drops to zero, so does control effectiveness in a non-vectored-thrust jet (aerobatic prop aircraft may have very limited control, due to propwash). If you've got pure vertical ascent, there is nothing to determine which way the aircraft will flip around. If you're lucky you'll just flip vertically downwards, oscillate a bit, and then recover. If not, you might spin, upright or inverted, or get into some sort of sustained deep stall. Regardless of what happens though, at the top you've put the aircraft into a situation that it isn't expected to operate in, with regard to both AoA and g, soon followed by rapid changes in pitch and quite possibly yaw, and engine cutouts would seem a distinct possibility.

[fjacobsen]

At least Compressor stall seems ti be simulated - what to complain about ?

When doing silly things - expect silly behaviour.

[spidierox]

At first I didn't want to get into a post which appearently is more important who is the whiner / complainer and things like that then actually listening to the OP.

I too was surprised that in a vertical climb after T/O (let's say I took unrestricted climb very loose here) I lost both engines. I wasn't expecting that.
I mean, with the F16 - F18 - F14 I don't recall that happening. The only thing is that you could stall the aircraft.

Now we know the F14A had flame out issues, so I was wondering is there also an inherent problem with the F15 ?  I did not see any warning in the manual about it
so is this normal behavior? on the other hand I can imagine that going vertical you don't have a good flow of air into the engines and you get the flame out.
I think this is more what the OP was curiuos about and so am I ...only learning the F15...

Edited June 29, 2023 by spidierox

[draconus]

45 minutes ago, spidierox said:

on the other hand I can imagine that going vertical you don't have a good flow of air into the engines

Why would it be any different to a level flight wrt air flow? The airspeed and AoA are of the main concerns here.

I went vertical but my engines didn't flameout. Maybe you were a bit over 90 degrees?

[Tenkom]

Could it be a 0g issue? Like in the A-10C where the engines shut down after x amount of seconds flying upside down.

Flying straight up for and extended amount of time might cut of supply of something for the engine.

[spidierox]

I was vertical ...honestly I was in VR and looking how fast I was going through the clouds and gaining altitude , full afterburner...awsome.

So I will do the same and watch airspeed and AoA now... instead of looking outside...

 

[IndyNavy]

This happened to me today. Climbed to 36,000 FT and flew upside down for a bit. Potentially a compressor stall or fuel flow issue. Def something we should keep testing...

[Rainmaker]

11 minutes ago, IndyNavy said:

This happened to me today. Climbed to 36,000 FT and flew upside down for a bit. Potentially a compressor stall or fuel flow issue. Def something we should keep testing...

Why would you test?  It's intentionally modeled that way.

[Nealius]

At what speeds? I've regularly done 90-degree climbs up to the 30s and 40s in both the Mudhen and A Tomcat, and I've never had engine issues in either one. I always roll inverted and pull to level off once airspeed decays below 300, at most 250. 

Edited September 24, 2023 by Nealius

[Rainmaker]

1 hour ago, Nealius said:

At what speeds? I've regularly done 90-degree climbs up to the 30s and 40s in both the Mudhen and A Tomcat, and I've never had engine issues in either one. I always roll inverted and pull to level off once airspeed decays below 300, at most 250. 

 

It becomes a factor when 0 - negative Gs are held past a certain time.  IRL, it's never a guarantee that it would happen.  In DCS, it limits people from doing a bunch of silly things.