investigating Thrust to weight ratio: confused

[bkthunder]

I flew the MiG-29 quite a bit lately and enjoying the FM overall. 

However, while I read and hear everyone saying it has the best T/W ratio in game, I have the opposite experience. 

I test flew it, flying close to the ground at low speed (~150kts) and then going into a full A/B "vertical" climb, the aircraft doesn't accelerate. At low altitude where engine thrust is maxed, if T/W ratio is >1 it should indeed gain speed as it climbs, instead the MiG-29A bleeds speed. 

I have run the same test on F-15 and F-18, and they both slowly gain speed up to about 5000ft, where engine thrust seems to decrease to the point of being less than the weight of the aircraft, and airspeed starts to decrease. 

In all cases I am talking about clean aircraft with 50% fuel.

 

 

Then I read the DCS MiG-29 manual and I find this: 

 

So, the DCS manual says the aircraft is 10900 kg empty, and the maximum thrust is 8300 Kg. 

According to the manual the DCS MiG-29 has a empty T/W ratio of 0.76. 

I think that's for a single engine, so 16600Kg in total. a T/W ratio of  1.52

 

I have looked around and pretty much all sources I could find, from wikipedia (I know...) to "From Farnborough to Kubinka - An American MiG-29 Experience Benjamin S. Lambeth" state the A/B static thrust to be in the range of 18200 lbs or about 8200 Kg. So in line with the manual

Why then in game the performance seems underwhelming? 

 

 

Update 9/15/2021

 

I performed several tests and recorded the data with Tacview. 

 

Test 1: 

At sea level and in Full A/B, initiate a constant 3g pull at 300Kts(CAS) up to an attitude of 80 degrees. Record altitude at 300, 250, 200, 250 and 100kts intervals. 

Each test performed 3 times for each aircraft, the numbers you see are the average values of the 3 tests. 

 

 

It appears that the MiG-29A is the worst performer while the F-16 is the best, with the F-18 a close second.

 

 

Test 2: 

At sea level and in full A/B, initiate a high alpha pull up at 200kts, up to an attitude of 70 degrees. 

With a T/W ratio of 1.2 for each aircraft, I expect each airplane to be able to accelerate vertically at low altitude. 

This is proven correct for the F-18, F-16 and F-15: they all gain a few knots from 200 up to 213-215 while climbing at 70 degrees pitch. 

The speed starts to decay after passing 6000ft for all aircraft. 

 

For the MiG-29A it's a different story: given the same conditions above, the speed drops immediately as the attitude of 70 degrees is set. The aircraft is never able to gain nor to maintain speed in a 70 degree climb at any altitude.

 

Each test performed twice for each aircraft. 

 

 

I attach here the tacview file. 

The trk exceeds the allowable file size, can you suggest a sharing service that doesn't require to sign up?

 

 

 

 

 

 

 

 

Tacview-20210915-175010-DCS.zip.acmi

Edited September 15, 2021 by bkthunder

[Mateo]

Usually static thrust parameter is the engine parameter - one engine, not all powerplant of aircraft. Regarding Thrust to Weight ratios your flight test of vertical climb is not appriopriate, as on high angle of attack, your lift to drag coefficient (L/D) may vary with different aircraft. In such test you took into account forces: weight, thrust, and you forgot about acting forces: lift and drag. If you would like to perform such test, I would suggest take-off-roll time and distance to chosen speed for example: 185 kias, it will also do not show correct numbers but will be much closer to judge T/W ratios.

Edited September 6, 2021 by Mateo

[draconus]

8 minutes ago, Mateo said:

I would suggest take-off-roll time and distance to chosen speed

I'd avoid adding ground friction to the equation as it's known to be different for some modules.

[sylkhan]

On 9/5/2021 at 8:10 PM, bkthunder said:

Why then in game the performance seems underwhelming?

Good question.

In DCS, some are overperforming, like F-18 and F14 (i remember reading french pilot telling how easy it was to win a dogfight vs the big F14), and some are underperforming, like Mig-29.

Why ?

mmmh.. i have some ideas, but....

Edited September 6, 2021 by sylkhan

[nighthawk2174]

4 hours ago, sylkhan said:

Good question.

In DCS, some are overperforming, like F-18 and F14 (i remember reading french pilot telling how easy it was to win a dogfight vs the big F14), and some are underperforming, like Mig-29.

Why ?

mmmh.. i have some ideas, but....

 

Need to be clear though if its an F-14A that may be the case especially if flown by newer pilots.  The F14 is not a plane you fly well quickly and without a lot of practice.  Currently thrust wise we know that the A is overperforming in mil and underperforming in AB.  B was about right although a change a few months ago had a knock off effect that had a bunch of effects on its FM that they are fixing.  As far as i'm aware the MIG-29 is more or less right, it even went through another FM revision sometime last year or earlier this year.

Edited September 7, 2021 by nighthawk2174

[Lurker]

15 hours ago, sylkhan said:

Good question.

In DCS, some are overperforming, like F-18 and F14 (i remember reading french pilot telling how easy it was to win a dogfight vs the big F14), and some are underperforming, like Mig-29.

Why ?

mmmh.. i have some ideas, but....

 

 

Trolling attempt 4/10

Edited September 7, 2021 by Lurker

[BIGNEWY]

Hi all, 

 

if you think there is a bug please add track replay examples of your tests. 

 

Feelings wont cut it for bug reports. 

[sylkhan]

11 hours ago, nighthawk2174 said:

Need to be clear though if its an F-14A that may be the case especially if flown by newer pilots. ....

 

It was in 2002, certainly against F-14D Super tomcat, flown by pilots from USS Theodore Roosevelt and  C. Stennis.

[GGTharos]

On 9/5/2021 at 2:10 PM, bkthunder said:

Why then in game the performance seems underwhelming?

 

The slow speed power curve on those engines isn't terribly impressive last I looked.  But I could be wrong.

[Spurts]

On 9/7/2021 at 9:32 AM, sylkhan said:

It was in 2002, certainly against F-14D Super tomcat, flown by pilots from USS Theodore Roosevelt and  C. Stennis.

 

You do know that even when the cat were retired there were more As in service than any other type, right?

[Cmptohocah]

I don't really have many FF modules, but in FC3 MiG-29 in full AB is like a rocket, compared to Flanker for example.

 

I am talking purely about a subjective feeling.

[Wizard_03]

Yeah idk about this thread, for me when I'm cooking along at max AB I need almost full forward trim and some forward stick deflection just to keep it from going into orbit. 

 

Seems like it has the best T/W in the game from where I'm sitting. F-14A/B, 15, 16, 18, su-27/33, and mirage don't even come close, in the acceleration department. So if it is under performing I don't think it really matters all that much you still have power in spades. 

 

Doesn't seem underwhelming for me at all.

 

Edited September 11, 2021 by Wizard_03

[Apok]

Its harder to slowdown then accelerate in Fulcrum. This is first time I hear someone thinks it is underperforming. 

Edited September 11, 2021 by Apok

[bkthunder]

Please see the first post, I updated it

[Cmptohocah]

3 hours ago, bkthunder said:

Please see the first post, I updated it

I am not an expert, but you need to remove drag from the equation in order to check T/W ratio. I mean, if you mount MiGs engines on a sphere that is the same weight as the MiG you will have the same T/W but the performance will be different since a sphere has much higher drag coef. than the actual plane.

[GGTharos]

But this is looking more like an FC3 vs. new aircraft turning.   The F-18 and F-16 should be losing thrust much faster than the fighters with variable ramps in those climbs.

[Cmptohocah]

I guess the only wayt to test T/W in DCS is to somehow have the airplane in vertical (like a space rocket), at sea-level and with full after-burners on.

If it starts climbing, then its T/W is indeed greater than one and the rate of climb would indicate how much it is. Or rather vertical acceleration.

[GGTharos]

Well, if you consider testing like this alone, you're exactly right, you have to somehow remove drag from the equation.

But, you can't even really guarantee that the thrust you're getting is correct.

 

So, at slow speed drag is pretty much not that big of a deal, right?  But at the same time the motors lose a lot of thrust when installed and at slow speed.

 

What we do have or well, ED has for the F-18 and F-16 are acceleration charts.  The eagle and miG-29 have them too, and I'm sure those two aircraft match their charts quite well.  I don't know about the other two though.

[bkthunder]

7 hours ago, Cmptohocah said:

I guess the only wayt to test T/W in DCS is to somehow have the airplane in vertical (like a space rocket), at sea-level and with full after-burners on.

If it starts climbing, then its T/W is indeed greater than one and the rate of climb would indicate how much it is. Or rather vertical acceleration.

Exactly, and that’s what I tried to do with test 1 and test 2. 
Especially in test 2 I put the aircraft at low speed and almost vertical. Low speed means drag is less relevant (drag increases with square of speed) and by being nearly vertical in both tests I tried to rule out lift as much as possible. 

Either way, the difference between the Mig-29 and F-18 is massive, and this doesn’t go well with the widespread knowledge/legend that the Mig-29 has a massive advantage in thrust. 
The F-15 also looks weak compared to the F-18 and F-16.

[Exorcet]

1 hour ago, bkthunder said:

Exactly, and that’s what I tried to do with test 1 and test 2. 
Especially in test 2 I put the aircraft at low speed and almost vertical. Low speed means drag is less relevant (drag increases with square of speed) and by being nearly vertical in both tests I tried to rule out lift as much as possible. 

Either way, the difference between the Mig-29 and F-18 is massive, and this doesn’t go well with the widespread knowledge/legend that the Mig-29 has a massive advantage in thrust. 
The F-15 also looks weak compared to the F-18 and F-16.

You could also try the ground roll test suggested above. Or cutting the engines at high speed at a given altitude and using the deceleration to measure drag directly. You could then do the opposite and accelerate at that altitude and work out thrust (not exactly, but it should be close).

 

Quote

Either way, the difference between the Mig-29 and F-18 is massive, and this doesn’t go well with the widespread knowledge/legend that the Mig-29 has a massive advantage in thrust. 
The F-15 also looks weak compared to the F-18 and F-16.

I haven't performed tests like those you have, but anecdotally the F-16 seems to vastly outperform everything in the transonic except maybe the F-14B. I've never noticed the F-18 to be particularly good, but I usually test with stores on. The MiG is dominant at high speed though, above Mach 1.5 or so the acceleration just becomes ridiculous. Something that seems odd about the F-15 is that in level flight it accelerates well, but even a shallow climb hurts it more than the F-16.

[Cmptohocah]

13 hours ago, GGTharos said:

So, at slow speed drag is pretty much not that big of a deal, right?  But at the same time the motors lose a lot of thrust when installed and at slow speed.

Thrust-to-weight ratios are given for max. weight and installed engines at sea-level altitude, so basically "static thrust". Pretty much all the engines are rated for this condition, as far as I am aware.

[GGTharos]

Engine thrust is given a bench thrust, I don't recall any public source calculating T/W from anything else.

[Wizard_03]

Empty T/Ws with AB

 

F-15C - 1.69

X2 F100-PW-220 @ 47540lbs combined

empty weight - 28000lbs 

 

 

F-16C BLK 50 no CFTs - 1.58

X1 F110-GE-129 @ 28984lbs

empty weight - 18238lbs

 

 

F/A-18C - 1.53

X2 F404-GE-402 @ 35400lbs combined

empty weight - 23000lbs

 

 

MiG-29A - 1.51 

X2 RD-33 @ 36680lbs combined

empty weight - 24251lbs

 

 

 

Sources: wiki/F-16.net

 

Take these with a grain of salt but it seems I was wrong the MiGs perceived performance advantage may have a lot more to do with lift then thrust. Very interesting. 

 

(F-15 though  lol)

 

 

Edited September 16, 2021 by Wizard_03

[Cmptohocah]

55 minutes ago, Wizard_03 said:

Take these with a grain of salt but it seems I was wrong the MiGs perceived performance advantage may have a lot more to do with lift then thrust. Very interesting. 

 

(F-15 though  lol)

You are correct. It has to do with lift-to-drag ratio. That's how airplanes that don't have T/W higher than one, get up in the air.

For example, if you deploy an air-brake on the F-15 it will still have the same T/W ratio, but it won't fly as fast.

[Wizard_03]

If we use the gross weights listed on Wiki

 

both MiG-29A and F-16CM Blk50 have: 1.11 T/W