Wrong Performance

Hi,

I did a test with the max available torque performance chart and the DCS Huey still has a huge error compared to the real thing.

I tested it at 0ft pressure altitude and 20°C FAT. The result was 44lbs torque.

At 44lbs torque, the huey's engine exploaded after 2 minutes.

Attached a track.

I thought they put the model at max 3% error with real charts... I guess they were wrong ;)

Performance chart bug.trk

OK, new test but with 0°C and same readings!!!

So the simulation is not taking into account ambient temperature.

Attached track.

Performance chart bug 0°C.trk

So the simulation is not taking into account ambient temperature

As you will note - the EGT was about 20°C less at 0°C for the same 44 psi Torque setting, so EGT may take the ambient temperature into account, however - it's hard to be certain as the Gas Producer RPM was also less.

Although EGT's are lower in the 1.5.8 update, they still seem at least ~35°C too high, so your 44 psi torque = EGT 660°C @ 0°C FAT and 680°C @ 20°C = engine failure in DCS as the temperatures are outside 610-625°C 30 minute limit.

If 44 psi = 30 minute EGT limit ?, I guess EGT should be 35-55°C less (or the torque read higher) ?

Given your Huey flying time, what would you expect the EGT to read in RL ?

Given your Huey flying time, what would you expect the EGT to read in RL ?

Hi Ramsay.

Between 615 and 620°C EGT should be the mark.

That's actually coherent with the operators manual MAT charts.

hmm..can you give us such a manual?

The TM we all have

http://milviz.com/Online_products/Manuals/UH-1H_Flight_Manual.pdf

Im not sure why you ask, the MAT chart refers exactly to EGT limits.

PilotMi8 said:

hmm..can you give us such a manual?

I believe both Piston85 and Gunnars Driver are of the opinion that the 30 minute Max Torque Available Altitude limits in TM 55-1520-210-10, page 280 are a direct result of reaching the 30 minute 610-625°C EGT limit i.e.

So with

• FAT = 11°C
• Torque = 45psi
• Altitude = 6000 ft

or

• FAT = 31°C
• Torque = 45psi
• Altitude = 0 ft

EGT would be 625°C

While I can't be certain that they are correct, Piston85 has flight time in the Huey and IMHO EGT will not be higher than the 30 minute EGT Limit at the charted Max Torque/Altitudes.

Yes, that is exactly what this chart is for.

In fact there is a note in the manual that says the following:

NOTE

Torque available values determined

are not limits. Any torque which can

be achieved, without exceeding

engine, transmission, or other limits,

may be used.

This is due to the fact that with these MAT values you may actually get colder EGT that the actual 30 minutes one.

Thanks.

Yes, that is exactly what this chart is for.

 

In fact there is a note in the manual that says the following:

 

NOTE

Torque available values determined

are not limits. Any torque which can

be achieved, without exceeding

engine, transmission, or other limits,

may be used.

 

 

This is due to the fact that with these MAT values you may actually get colder EGT that the actual 30 minutes one.

 

 

 

 

Thanks.

Exactly. Spot on!

The main reason for this is that engines are indiviuals when it comes to performance, and new engines without wear/damages make more power within the limits( NG, EGT)

The charts are made up so they still are valid for an engine barely making the maximum power test.

Maintenance test flights normally includes a power test to assure that the engine can deliver the correct power. In most cases a power margin for gas generator and turbine is calculated. Normal values with good engines for the helo types I act/acted as a MTP is 104-110%, meaning that the engine can deliver 4-10% more than the minimum specification and still be within EGT/T4 and Ng limits.

I once made a OEI flight in hot and high environment to check that the numbers in the charts was valid. First flight the maximum alt on one of the engines was virtually spot on. The second flight on the other engine, the max alt was clearly higher than the calcution, after checking the calculation again the history for the power margin confirmed that the other engine had a big power margin while the first only had a small one.

Wy do I tell this? Well, if BST adjust the values for EGT and someone finds that he actually could use more power than the ”maximum power available” charts, this is the reason.

A helicopter correctly maintaned and that is ok can have a little better performance than the chart but not worse than the chart. The EGT is the limiting factor for the available power on UH-1H in this charts and should meet the upper 625C limit at or slightly above ”maximum power available” charts.

May be a dumb question, but do we have the 314 Rotor used, or the 324?

May be a dumb question, but do we have the 314 Rotor modeled, or the 324?

324

We've always used the 324 chart, I think Ramsay used the 314 one just this time.

May be a dumb question, but do we have the 314 Rotor used, or the 324?

324

 

We've always used the 324 chart, I think Ramsay used the 314 one just this time.

For your information it is not a question of different rotors. It is the rotor rpm, most often called NR, at least nowadays !

You can beep the rotor rpm in the module also, and 324 rpm is the prefered rpm to use for low speed and hover( more lift). I didn't fly the UH-1 for more then a handfull of flights( never trained on the type) but I know at least with our Hueys the normal was to beep down NR during cruise and beep up before landing.

Of course both rotor rpm is possible to use in the module so both should be correct mapped in a "perfect module" :-)

For your information it is not a question of different rotors. It is the rotor rpm, most often called NR, at least nowadays !

 

 

You can beep the rotor rpm in the module also, and 324 rpm is the prefered rpm to use for low speed and hover( more lift). I didn't fly the UH-1 for more then a handfull of flights( never trained on the type) but I know at least with our Hueys the normal was to beep down NR during cruise and beep up before landing.

 

 

Of course both rotor rpm is possible to use in the module so both should be correct mapped in a "perfect module" :-)

I think you are right EGT is still a bit too high, at the moment.

I guess the problem is to tweak the engine model to behave 99% correct, as you cannot simply enter a "required EGT" as the modeling is dynamic...

Ok, so you used the Governor at fixed value with the 324/6600 RPM.

I think you are right EGT is still a bit too high, at the moment.

I guess the problem is to tweak the engine model to behave 99% correct, as you cannot simply enter a "required EGT" as the modeling is dynamic...

At sea level up to 20C-ish( didn't look at the chart for this post) you should hit the red line on the torquemeter at 50PSI-ish(if its modeled at 50PSI) before you hit the EGT 625C.

We've always used the 324 chart, I think Ramsay used the 314 one just this time.

Yes, my bad, I copy and pasted the wrong chart from the Flight Manual to annotate it in Photoshop, sorry about that. EGT Altitude Contours limiting Max Torque is the same though.

Edit: 324/6600 Chart updated - Max Torque/EGT Limits occurs at approx 4°C lower FAT's in the 324/6600 chart upto about 8000 ft, principle remains the same.

is the dcs uh-1 supposed to be equipped with metal or composite blades ?

is the dcs uh-1 supposed to be equipped with metal or composite blades ?

Both, even the manual clarifies the benefit if composite blades were installed.

From factory it was metal unless asked differently by the operator.

I think you are right EGT is still a bit too high, at the moment.

I guess the problem is to tweak the engine model to behave 99% correct, as you cannot simply enter a "required EGT" as the modeling is dynamic...

The trouble is the Torque/EGT relationship requires more than 'a little tweaking', it looks to require a lot of work.

For example, hot parking at Batumi with a overloaded UH-1H (112%)

• FAT= 0°C

• Altitude= approx 0 ft MSL

Max Torque = 40 psi to reach the 625°C EGT 30 minute Limit in DCS 1.5.8

From the 324/6600 chart

At 0 ft MSL, even if the helicopter can't takeoff, it should be the 50 psi XMSN Limit that prevents or is exceeded by the pilot to achieve takeoff not EGT.

The 40 psi EGT Limit we have at 0°C/0 ft in DCS 1.5.8 should equate to 12000 ft.

Edit: With Engine De-ice=Off, at 0°C/0 ft in DCS 1.5.8 - Max Torque = 51 psi to reach the 625°C EGT 30 minute Limit and equates to 6000 ft.

The trouble is the Torque/EGT relationship requires more than 'a little tweaking', it looks to require a lot of work.

 

For example, hot parking at Batumi with a overloaded UH-1H (112%)

 

• FAT= 0°C

• Altitude= approx 0 ft MSL

 

Max Torque = 40 psi to reach the 625°C EGT 30 minute Limit in DCS 1.5.8

 

From the 324/6600 chart

 

At 0 ft MSL, even if the helicopter can't takeoff, it should be the 50 psi XMSN Limit that prevents or is exceeded by the pilot to achieve takeoff not EGT.

 

The 40 psi EGT Limit we have at 0°C/0 ft in DCS 1.5.8 should equate to 12000 ft.

Yeap, although I think that considering they are just parameters numbers it should not be an overwhelming work to get this fixed.

What I dont understand is why BST thought it was accurately modeled according to their update statement of 2.3% error.

Both, even the manual clarifies the benefit if composite blades were installed.

 

From factory it was metal unless asked differently by the operator.

No, that was not the question.

The DCS UH-1H module, not the real UH-1, it the module supposed to have metal or composite blades ? ...to be able to use the corrext charts testing performance.

No, that was not the question.

 

 

The DCS UH-1H module, not the real UH-1, it the module supposed to have metal or composite blades ? ...to be able to use the corrext charts testing performance.

This guy says it is a composite module, but has no evidence of it.

https://forums.eagle.ru/showthread.php?p=1802728

The trouble is the Torque/EGT relationship requires more than 'a little tweaking', it looks to require a lot of work.

 

For example, hot parking at Batumi with a overloaded UH-1H (112%)

 

• FAT= 0°C

• Altitude= approx 0 ft MSL

 

Max Torque = 40 psi to reach the 625°C EGT 30 minute Limit in DCS 1.5.8

 

From the 324/6600 chart

 

At 0 ft MSL, even if the helicopter can't takeoff, it should be the 50 psi XMSN Limit that prevents or is exceeded by the pilot to achieve takeoff not EGT.

 

The 40 psi EGT Limit we have at 0°C/0 ft in DCS 1.5.8 should equate to 12000 ft.

I find 40PSI also now. Last time I checked, I think we both got 37PSI.

The engine EGT meter doesnt have the correct limits shown. It should be gren between 400 and 610(it is). It should be yellow between 610 to 625 and a red line at 625C. I cant se the read line in the correct place. Couldnt se any yellow field either but in VR so...

The available power is as you found much to low when the EGT is within limit. I tried to use 50PSI at the altitude /temp where EGT should reach the limit at 50PSI, but this resulted in an EGT of 700-705C.

From 0 to 6000 feet the available power was the same, 39-40PSI at EGT 625C. (OAT/FAT 20 at sea level and decreasing a little bit more than ISA).

Its clearly not following the charts for power, and the engine is not affected from density altitude in that range at all. At higher altitudes(checked 10.000 and 12.000 feet), power was affected.

I also checked the hover ceiling. Assumed metal blades. Loaded it up to 9500lbs and set oat for +15 at 2000feet, it should be able to hover OGE at +16. It should be a small margin. Well, at ground and +20C it couldnt hover OGE and only able to hover IGE at 20-21 feet(when keeping EGT =625).

So I accelerated and climbed to 2000 feet, and then I went for the 47,5-48PSI that the hover power required respective the power available chart say. This should also be the Hover ceiling. ( charts 7-13 to 7-15). When using 47,5 to 48 in hover, it could climb with around 500 fpm. This is not right either. To powerful, if the engine would give the right power (adjusted EGT) the climb seems to high.

Also, tried autorotation at different altitudes, up to 15000. IRL the autorotation rpm get higher in higher altitude, forcing you to have the collective higher to keep the rotor rpm within limits. In this case, the max rotor rpm was the same, and the collective in the same place at 1000feet and 15000 feet. Also, normally the cyclic gets rather sluggish at higher altitudes, specially at lower speeds. I did test his and I couldnt feel any difference from low altitude.

That said, I like the module a lot. Didn't fly the DCS UH-1 that much so far, but the feeling is great. Quite close to a real helo and very fun :-)

Gunnars Driver said:

That said, I like the module a lot. Didn't fly the DCS UH-1 that much so far, but the feeling is great. Quite close to a real helo and very fun

Agreed, the UH-1H is a great module, though I tend to fly the Gazelle ATM (despite it's issues) due to multi-crew and having bought a second copy for my son.

On topic - I placed a few FARP's at different altitudes to try to map the DCS UH-1H MAT, though my data is very rough, it should give a fair idea of the major features of the current EGT/Torque model.

It seems the 0 ft EGT is about 5500 ft out for the FAT.

̶a̶b̶o̶v̶e̶ ̶1̶0̶°̶C̶,̶ ̶h̶o̶w̶e̶v̶e̶r̶ ̶i̶t̶ ̶l̶o̶o̶k̶s̶ ̶l̶i̶k̶e̶ ̶t̶h̶e̶r̶e̶ ̶i̶s̶ ̶d̶i̶s̶c̶o̶n̶t̶i̶n̶u̶i̶t̶y̶ ̶i̶n̶ ̶t̶h̶e̶ ̶E̶G̶T̶ ̶m̶o̶d̶e̶l̶ ̶a̶r̶o̶u̶n̶d̶ ̶F̶A̶T̶=̶7̶°̶C̶ ̶t̶h̶a̶t̶ ̶i̶n̶c̶r̶e̶a̶s̶e̶s̶ ̶E̶G̶T̶'̶s̶ ̶f̶o̶r̶ ̶l̶o̶w̶e̶r̶ ̶F̶A̶T̶ ̶t̶e̶m̶p̶s̶ ̶s̶u̶b̶s̶t̶a̶n̶t̶i̶a̶l̶l̶y̶.̶

Hopefully BST are already on it or my post might give them a pointer to what's wrong.

Edit:

The discontinuity in the EGT at FAT=5°C in the original chart was due to an error on my part (spawning a UH-1H at OAT 5°C and below, defaults Engine De-Ice=On and must be turned Off) - the chart has been updated with the corrected measurements.

Turning off the De-ice removes the discontinuity and the EGT is consistent with the higher FAT temperatures i.e.

• 0 ft, FAT 5°C = 49 psi Max Torque
• 0 ft, FAT 0°C = 51 psi Max Torque

I wonder what kind of timeframe we can expect from BST considering that implementing EGT limit took them a couple of years. And it didnt even come out well. Perhaps it is more difficult than we think.

Dont get me wrong, its not a negative comment rather than a fact, I just wish the Huey was able to be used as a real training simulator.

Yeap, although I think that considering they are just parameters numbers it should not be an overwhelming work to get this fixed.

That is what I meant. From what I've learned it isn't just "parameters numbers" it is "change a parameter, check everything and see what the dynamic model gives as a result in ALL flight areas" then rinse and repeat.

That is to be done and tested for different environmental conditions as well.

Most DCS models use dynamic parameters, fed from the World "engine" and dynamically calculate the actual flight behaviour (FM) from that.

If you tweak a couple parameters to match torque and EGT limits you may end up with dozens of other things in the flight model being wrong.