EGT limits in UH-1H - Page 24 - ED Forums
 


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Old 01-15-2018, 08:00 PM   #231
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Originally Posted by Piston85 View Post
This could also be that the torque reading is false and we are actually having the correct value modeled. BUT, if that is the case then the performance of the engine at that torque is waaaay too low.


Thanks.

No it can not.


The red line is supposed to be the transmission max torque limit( = 1100 hp)
The engine is flatrated to 1134hp. This means that the engine should produce slightly over the red mark/50PSI on the torque meter befor the NR starts to drop( as long as engine power is sufficient the rotor rpm do not drop).


If the red line is at 50PSI( correction factor/torque meter shows correct value) the engine should be able to pull 51.5PSI before the engine/rotor rpm droops significant at least at low altitude and temperature. I think I have seen it around the 50PSI mark, maybe slightly above, telling us that the engine pulls the power it should and that the torque meter shows about the correct value for this.


Of course, its a game and you actually can call it everything wrong( for example both the engine to weak and the torque meter wrong but by coincidence it happen to show the torque when the engine/rotor droops at the correct value. But no, I think we should find those things that are ok, and plays well together with other values. After this BST only fix the small things that makes the module even greater.
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Old 01-15-2018, 09:16 PM   #232
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Originally Posted by Gunnars Driver View Post
The engine is flatrated to 1134hp. This means that the engine should produce slightly over the red mark/50PSI on the torque meter befor the NR starts to drop( as long as engine power is sufficient the rotor rpm do not drop).
As transmission failure/damage isn't modelled in DCS, should we not be able hit the same torque limits (60/64 psi) as measured in the engine test cell if we can load the rotors sufficiently ?

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Originally Posted by Gunnars Driver View Post
I think I have seen it around the 50PSI mark, maybe slightly above, telling us that the engine pulls the power it should and that the torque meter shows about the correct value for this.
The maximum torque I recorded in DCS 1.5.8 was 58 psi (0 ft, -10°C OAT, 590°C EGT, De-ice=OFF, *Low Rotor RPM warning and Full Collective - note: I didn't try increasing the governor).

The highest RL flight torque I've seen recorded were 66 psi transients (-4800 ft, -27°C OAT, 314 RPM) in "Operational Use of the UH-1H Helicopters in Arctic Environment, ADA002603" i.e. during hover and ascent in extremely cold conditions. AFAIK they were atypical of the rest of the flight data.

Edit:
For Info: 58 psi @ 6300 RPM (Low RPM Limit) = (310*20.38306)*(-18.83+19.05*58 )/5252.113 = 1307 shp

Last edited by Ramsay; 01-15-2018 at 11:52 PM.
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Old 01-15-2018, 10:18 PM   #233
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Originally Posted by Gunnars Driver View Post
No it can not.


The red line is supposed to be the transmission max torque limit( = 1100 hp)
The engine is flatrated to 1134hp. This means that the engine should produce slightly over the red mark/50PSI on the torque meter befor the NR starts to drop( as long as engine power is sufficient the rotor rpm do not drop).


If the red line is at 50PSI( correction factor/torque meter shows correct value) the engine should be able to pull 51.5PSI before the engine/rotor rpm droops significant at least at low altitude and temperature. I think I have seen it around the 50PSI mark, maybe slightly above, telling us that the engine pulls the power it should and that the torque meter shows about the correct value for this.


Of course, its a game and you actually can call it everything wrong( for example both the engine to weak and the torque meter wrong but by coincidence it happen to show the torque when the engine/rotor droops at the correct value. But no, I think we should find those things that are ok, and plays well together with other values. After this BST only fix the small things that makes the module even greater.

As usual, you didnt understand my post.

I said that maybe in the background the torque is right and we are just seeing the wrong reading in the game's gauge.
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Old 01-15-2018, 11:47 PM   #234
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Originally Posted by Ramsay View Post
As transmission failure/damage isn't modelled in DCS, should we not be able hit the same torque limits (60/64 psi) as measured in the engine test cell if we can load the rotors sufficiently ?

No, the engine is derated to 1134hp according to the official Bell manual, so it should keep the rotor rpm until we reach this number....which should be around 51.1PSI if the red line is marked on 50 exactly. In real life when mounting the engine the max fuel flow is set to 1134hp. If the Bell manual is correct the torque shouldnt go above this. If you increase the collective further the rotor rpm will decay.


This is a standard practise on a lot of helo engines, but on single engine helos most cases much higher than the xmsn limit(giving the pilot the possibility to overtorque the xmsn if needed instead of risk a crash etc.).
On multiengine helos often the xmsn can stand more than the engine can deliver. When max power is reached the torque doesnt increase when applying more collective but the rotor rpm decay.


just tested the Engine anti icing. On ground Delta about 25 degrees, seems fair engough. In hover with hover power ~ 80 degrees
C which just cant be true. when using a lot of power the EGT normally doesnt show that
much difference. It doesnt become more than at flat pitch ground.
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Old 01-16-2018, 05:11 AM   #235
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As transmission failure/damage isn't modelled in DCS
Sorry for digressing, but are you sure? Because flying the Mi-8, I at least think I've seen occasional transmission fires and resultant malfunctions etc. after a well-placed hit or two.
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Old 01-16-2018, 01:19 PM   #236
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Sorry for digressing, but are you sure?
I'm not 100% sure damage due to over torque isn't modelled, as exceeding 50 psi torque in DCS is difficult (unless deliberately trying) and outside normal parameters.

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Because flying the Mi-8, I at least think I've seen occasional transmission fires and resultant malfunctions etc. after a well-placed hit or two.
The Mi-8 is a different beast, was released after the UH-1H, inherits some features from BST's full cockpit simulator, etc. - so might well incorporate transmission failure due to over torque. I haven't seen it myself but haven't flown the Mi-8 as much, either.

Over torque (like wing over g) involves exceeding the normal range of elasticity (stuff gets bent), accelerated wear, etc. rather than exploding into fire, etc. (though a collapsed bearing can overheat and set fire to the oil). There are also often engineered weak points, so a transmission fails safely - without destroying an aircraft. As DCS is often seen as a 'combat' only simulator, it's unlikely such details are modelled but not impossible.

Transmission damage due to weapons fire would be a different damage model.

Last edited by Ramsay; 01-16-2018 at 01:28 PM.
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Old 01-16-2018, 01:46 PM   #237
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I know, I just thought you thought there's no transmission / powertrain DM whatsoever. Anyway, sorry for the slight digression, please continue
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Old 01-16-2018, 06:54 PM   #238
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I'm not 100% sure damage due to over torque isn't modelled, as exceeding 50 psi torque in DCS is difficult (unless deliberately trying) and outside normal parameters.

Over torque (like wing over g) involves exceeding the normal range of elasticity (stuff gets bent), accelerated wear, etc. rather than exploding into fire, etc. (though a collapsed bearing can overheat and set fire to the oil). There are also often engineered weak points, so a transmission fails safely - without destroying an aircraft
As far as the manual states, if engine only prodeces just above the xmsn limit, overtorques should be rare.

Overtorque is exceeding the normal design load limit for that part amount of hours between maintanence. Most transmission have an extra margin, often in different steps.
Think I saw this in the huey manual also. Most cases its torque up to x seconds in these steps.
For the Bo105 I remember it was a quite small margin on one engine inoperative( power input to mgb limiting) only 3 counts of overtorque on one engine(even very small overtorque), after 3 such the mgb had to be overhauled.

For transmission I never heard of making weak points( smaller units like generators connection shafts can have manufactured weak points to not stop the engine if seizes), but for the transmission itself I newer heard of this.

For the transmission itself I would say you have only one and they dont make any weak points by purpose.
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Old 01-16-2018, 06:59 PM   #239
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As usual, you didnt understand my post.

I said that maybe in the background the torque is right and we are just seeing the wrong reading in the game's gauge.
Do you understand the analogy that if the torquemeter reads 51.5 when the engine delivers its maximum performance at Sea level +15c either the torque and the engine is ok ir both are not ok ?
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Old 01-16-2018, 08:12 PM   #240
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I just realized how much off topic we've made here

I hope BST keeps track of the good posts there are here.
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