F-15 Strike Eagle (C, D, E & I) Official Community Mod

User Support Hub Aircraft & Systems
41

Hi Guys,

As I understand, you are talking about a sustained (or coordinated) turn. In my understanding that means:

  • speed is constant
  • vertical speed is constant zero
  • bank angle (Theta) is constant
  • AOA (Alpha) is constant, below stall AOA (!)
  • the only thing changing is the position of the plane in the universe (except for those who are the middle of the universe)

In such sustained turn the g-load is only dependent on the bank angle Theta acc. to this simple formula:

G-Load = 1 / cos Theta.

This aplies to any speed.The G-load is not (!) dependent on speed. It is also not (!) dependent on weight. Higher weight will result in higher speed. If that is constant (sustained flight), the fomula above still applies.

SilentG37’s diagram confirm this. There is a constant relation between g-load (left scale) and bank angle (right scale). The variable parameter in the diagram is the speed necessary for a sustained turn.

Some examples for different bank angles:

Theta 30 deg → 1.2 g
Theta 45 deg → 1.4 g
Theta 60 deg → 2 g
Theta 78 deg → 5 g
Theta 84 deg → 9.6 g

Flying at higher loads than 9 g, the plane will disassemble, long after the pilot lost consciousness.

Flying at g-loads higher than 9 g (assuming the pilot and the aircraft could withstand it) is not a sustained flight (see prerequsites above) any more. Higher g-loads can be flown only in dynamic manouvers where the parameters are not constant any more.

For sustained flight up to Theta=75, I think Jack’s model perfectly represents reality.
Beyond that, maneuvers become dynamic (not sustained any more). It’s hard to maintain the paramters at bank angles higher than 75°.

Perharps Dean should implement a pilots black out function where screen will get dark at g-loads above pilots limit.

In modern fighters a digital flight control system prevents the pilot from exceeding max g-load and max alpha.

6 Likes
42

@jdiegel54 thanks again for your expertise! Couldn’t make this plane the way it is without you and the other testers input and hours of testing!

1 Like
43

In reality, any aircraft can sustain much higher G-loads than they’re supposed to. The difference is that in reality, any attempt to do so would rip the wings off :slight_smile: Even if it didn’t, the aircraft would be grounded afterwards for inspection, as would any aircraft that exceeded POH limitations.

We don’t have a way yet to simulate induced G-blackout, but it’s certainly something that I would like to see in the future to avoid these scenarios. I’m planning to include compressor stalls in the F-14A if people are too heavy with the controls, so I might think about similar failures in the F-15 if they exceed the design limitations.

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44

I appreciate the implementation of any unfriendly behavior of the aircraft, punishing the pilot for bad airmanship.
Compressor stall would be great.
That’s realism, and realism is fun.

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anyway I was allowing more G on purpose while developing the flight model. currently in the flight model we had the Max G. at 12, multiplied by a safety factor of 1.8: which allowed us to do 20G without problem. We have been doing tests and we are going to leave it at 9 with a factor of 1.5. With which, a maneuver like a sharp pullback like that will suppose the structural damage when exceeding 14G, unless you deactivate the damages in the options.

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46

I agree, it’s too easy at the moment for folks to just burn around at silly speeds and pull manoeuvers that would not be performed in real life. I have to be careful and stay within my remit of “fun” over super-realism, but I think some sensible barriers would benefit the product and create that extra bit of realism, and maybe teach users a thing or two :slight_smile:

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47

Following your theory @jdiegel54 , if we drew an imaginary line to continue the curve at sea level, it would be as follows (correct me if I’m wrong):

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48

I agree, your red curve should be the natural curve not minding structural limits.
After flying that curve, assumed the pilot has an extraordinary anti-g-suit and doesn’t get a black-out, the plane has to go into the shop for structural inspection, as Dean said.
The diagram interestingly shows, that above an altitude higher than 10000 ft, in a sustained turn, the Eagle cannot be overstressed any more.

49

yeah but that is with 40000lbs.

with 42000lbs:

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with 62000lbs (full fuel):

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So, if the empty weight is 31700lbs and you loaded a minimum amount of fuel (let’s say you set 35000lbs), those curves would surely grow exponentially.

1 Like
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At the first look it seems contradictory that higher weight reduces the danger to overstress (talking about sustained turn only). The reason for that is, higher weight reduces the maximum bank angle which can be flown in a sustained turn, which also reduces g-load. Of course all that doesn’t apply for highly dynamic maneuvers.

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51

There’s always a safety margin. If a plane is rated to +9 Gs the wings aren’t just going to instantly rip off the moment 9.1 Gs is reached. Too bad physical destruction isn’t possible. I would love to see somewhat accurate results of wildly exceeding structural limits! Wings and/or control surfaces ripping off, fuel going everywhere, exploding. You know fun stuff!!! But it’s also nice to not have to restart because you just happened to pull on the stick too hard once or twice. I guess I’d like to see Asobo make three modes for such things. Disabled, warnings/notification, or just plain old “You broke your airplane! Your flight is over!”

I’d like black/red outs, but I’d also like them to be able to be toggled on/off.

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52

I enjoyed the graphic about the climb procedure to 90,000 ft.

I tried it and it worked well. Only item, when I leveled off, it was very difficult to turn
 guessing thin air. I ended up stalling and falling to 50,000 ft before I could even turn the plane and recover
I was going almost strait down with over 230 or so knots and it wouldn’t turn left or right even with afterburners on. Almost had to drop flaps to get some maneuverability. Probably just me, but it was a fun test !

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53

They put a RCS system on the NF-104 which was the F-104 variant with an additional rocket motor made for NASA to train astronauts to use an RCS system like spacecraft have. The air is indeed incredibly thin at 90K and those 100K+ flights were for all intents entirely uncontrollable at their peak altitude without the maneuvering rockets. Just no air for the control surfaces to act on.

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54

Keep an eye out from the mode team regarding an update to the mod soon. Made minor changes to flight model, hud layout/warnings, and some other things. Jack will have an outline of everything we changed here, once its posted to github.
Still just reviewing and testing ourselves, but sometime over the next couple of days. (But don’t hold me to this) The mod team including the testers all contribute in their own free time, as they can.

We are very excited about the changes and hope to bring them to you soon.

Silent

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F-15 (C/D/E/I) Official Community Mod v.1.16 update

Release v1.16 · F-15-C-D-E-I-Official-Community-Mod/dcdesigns-aircraft-f15_v1.0.1_rev_1.16 (github.com)

Change list:

  • Take-off/Landing speeds revision.
  • Further review of sustained level turns, and further explanation of what it is
  • Auto-retractable flaps (as per the manual at 250kts)
  • G Limit warning on all HUDs
  • Further HUD modeling directed by manual for each model

As always and with the invaluable help of our testers, we have made the following changes since 1.15i:

Reviewed take off min speeds, landing approach speeds, and nosewheel speeds for all models matching the real charts:

Models C/D:

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Models E/I:

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So, in order to achieve this, we adjusted the overall lift and lift vs flaps scalars to match the real data by using the following configuration:

C/D: Landing speeds per 35000lbs: No flap landing speed = 155kts - Full flap landing speed = 142kts per recommended AOA 8 degrees.

E/I: Landing speeds per 40000lbs: No flap landing speed = 168kts - Full flap landing speed = 154kts per recommended AOA 8 degrees.

This means: by following the tables attached above, based on the amount of weight loaded on the plane, you can calculate the required landing speed based on the recommended AOA of 8 degrees.

We also reviewed the pitch stability, in order to reduce nervous at input values near center and make the controls smoother than before.

In addition, with the adjustments made with the overall lift and the lift vs flaps, we also made some adjustments in the elasticity tables against dynamic pressures, and also some adjustments in the aerodynamics section in order to match the sustained turns in game with the real airplane:

Models E/I:

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Models C/D:

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So, you should be able to maintain sustained turns, keeping angular velocity at the supported speed and load factor as the actual graph.

Note: We have noticed on the forums that there is some confusion about what sustained turns mean relative to maximum G’s that an aircraft could produce during maneuvers, as well as maximum G limits before structural damage: sustained turns mean that an aircraft can maintain an angular velocity in degrees / sec for a certain speed and produce an amount of G without losing speed in the process. It does not refer to the maximum G’s that the aircraft could produce when pushing the entire flight stick back or forward (which is more than the max G allowed by the manufacturer). Both, we and our testers did several tests on the curves shown in the real charts, at different speeds, applying certain G’s controlling the pressure applied to the flight stick, managing to maintain the angular speed and linear speed, and they match with the real charts. Whether someone wants to overcome structural limits is up to the pilot.

What the real f15 has is a CAS system that can regulate or harden the flight stick path from 0.9 Mach (can be activated or not), but I don’t know if that can be implemented in MSFS (but we will look at it in the future). What may be improved is the smoothness of the stick and this is what has been done in this case, to have more authority in the joystick when making those turns without exceeding the maximum G to limit structural damage.

Once the calibrations have been carried out, the limit for aircraft structural damage has been set at 15.6G so as not to ruin your game. However, you should have no problem applying the correct input and force to your flight stick to get the correct numbers and values ​​below 12 G in tight turns or aerobatic maneuvers (let’s say 9g is just a manufacturer’s warranty to guarantee airplane health).

Implemented retractable Flaps at and above 250kts according the real model.

Little adjustments made in all MFD’s and HUD’s and also, implemented G-warning in the HUD’s when surpassing 9G’s:

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Instructions: just unzip the folder included in the zip into your community folder. Remove any previous mod you could have before. Official product and mod version must coexist into community folder this way:

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Our best regards to everyone and we hope you enjoy with the new version.

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56

Congratulations to the entire mod team, excellent work.

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I really appreciate it @jdiegel54. Your help has been extremely important from the beginning to get to where we are now and we couldn’t be more grateful for your contributions. We hope to continue learning from you every day and to be able to reflect it on this or any other plane.

:slight_smile:

3 Likes
58

Anyone with the same ILS GS issue
F15E ILS Landing
KTKX to KJBR ILS 110.15 RW23 - Perfect, lNS=DA on the left hand side of runway
EGVN ILS 108.55 RW07 on the numbers lenght wise, 50 feet left of runway on the grass
EGHH on the numbers lenght wise, 75 feet left of runway on the grass
KLMS to KMEI ILS 109.70 RW19 OK, Requires careful power management to keep the GS
09R to KOCH ILS 111.50 RW36 Just short of runway 150 feet left on the grass
YCDR to YBBN ILS 110.10 RW19L Perfect

Tested each one 5 times! Same results.

59

Interesting - the ILS system in the F-15s relies on the MSFS core program’s autopilot, so it sounds as though there is something wrong with either the ILS or perhaps some of the airports in MSFS, tough to tell which though.

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It is a shame, althought noones fault, but it would be wonderful if it worked. Strange I can get it to work on one aiport I have found, but not the others. Spent hours testing and trying thinks, even Jack is trying to help