Wrong Performance

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.

 

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

I dont know if the DCS itself could be a factor.

Density altitude,meaning thinner air when higher and/ or warmer, should affect both engine power and aircraft flight performance.

The engine: Higher density altitude should make exhast temp increase at same power output because the air mass flow decrease and you burn the same amount of fuel but less air = air gets warmer. Tinner air also should mean Ng/ gas producer rpm increase because same power driving it, but it takes less power to spinn it in thinner air. All of this is valid for all turbines and should be reflected in DCS/ this module.

Normally all turbine engines would produce the same power at higher altitudes if abused with too high T4/EGT, i.e 50PSI of torque( but the higher density alt the higher EGT). I did not find any info about the UH-1H engine fuel control reducing power by itself at increasing altitudes. This is possible but I newer seen such systems( have flown helis constructed from the the early 60:s to very modern fly by wire generation). My guess would be it does not reduce power by itself to keep EGT safe, but its not impossible. This part is important, because it tell us how the power and EGT react if we use more power than the charts.

The aircraft: higher density altitude means the rotor blades need higher angle of attack to produce the same lift. This increases the induced drag causing the need of power delivered from the engine to increase. The collective stick will need to be higher due to this. This is clearly notacible on all helicopter types I have flown. When lowering the stick, the point where the rotors autorotating will drive the rotor will be higher and with collective in bottom the rotor rom will be higher. Cyclic will also need bigger inputs att higher altitudes to get the same reaction( normally not that notacible at lower altitudes but higher up it is).

Both these ( engine, Aircraft) will need to be modeled to get flight caracteristics and performance to behave at least near to the real one. Its the law of nature and there is no way around it.

Cutting the post into two parts, making it easier to follow( I hope...)

The engine loss of power according to the above statements can be seen in the same chart we have posted numerous times, its also a few posts up( Ramsays post).

Higher altitude reduces available power*

Higher FAT/OAT reduces available power*

The aircraft performance can be seen in the chart Hover power required ( just behind in the manual).

Higher altitude increases required power.

Higher FAT/OAT increases required power.

The reasons in post above.

*) With [power available] manual is meaning available power still keeping related values within limits. For most turbine engines, if you abuse it, it’ll produce a lot more power, but the exhaust temp will be to high.

The flight model doesnt seem to have high altitude limits to the rotor system incorporated.

At high altitudes the VNE is much lower, due to much higher angle of attack on the blades, speccially the retrieting blade, causing the retreting blade to stall at lower indicated speeds.

I tried normal VNE( airspeed meter red line) at 10-12000 feet and despite some abuse it still continued to fly without problems. I guess the VNE chart ( airspeed operating limits) not is incorporated in THE DCS module. The flight test parameter for VNE is that manufacturer show a max safe airspeed and then reduce it to 90%, meaning it should be possble to fly 111% of VNE. If you go further away from this value, bad things is prone to happen...

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

 

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

Furia (post 64) here https://forums.eagle.ru/showthread.php?p=1721244

says composites. Very reliable.

Also see DCS Huey Fl Manual, page 10.

Furia (post 64) here https://forums.eagle.ru/showthread.php?p=1721244

says composites. Very reliable.

Also see DCS Huey Fl Manual, page 10.

Page 10 is what I said before, and it doesnt state anything other than the benefits of installing composite blades.

We will need BST to confirm this.

OK

Ramsay said:

It seems the 0 ft EGT is about 5500 ft out for FAT's above 10°C, however it looks like there is discontinuity in the EGT model around FAT=7°C that increases EGT's for lower FAT temps substantially.

The discontinuity in the EGT's at FAT=5°C 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) - I'll update the original chart once I've re-taken the all the measurements at OAT 5°C and below.

Turning Off the Engine De-ice removes the discontinuity and the measured EGT's are 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

Page 10 is what I said before, and it doesnt state anything other than the benefits of installing composite blades.

 

We will need BST to confirm this.

Yah, maybe you missed page 182 of the Fl Manual.

The discontinuity in the EGT's at FAT=5°C 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) - I'll update the original chart once I've re-taken the all the measurements at OAT 5°C and below.

 

Turning Off the Engine De-ice removes the discontinuity and the measured EGT's are 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

Anyway, nice work.

we figured out where we are wrong. We will correct! Thank you for helping!

key phrase - "30 MINUTE OPERATION"!:doh:

we figured out where we are wrong. We will correct! Thank you for helping!

key phrase - "30 MINUTE OPERATION"!:doh:

Enviado desde mi Moto Z Play mediante Tapatalk

we figured out where we are wrong. We will correct! Thank you for helping!:thumbup:

key phrase - "30 MINUTE OPERATION"!:doh:

Thank you! I am also very happy Huey get's some love, it is my most favorite module (Mi-8 being the second).

we figured out where we are wrong. We will correct! Thank you for helping!:thumbup:

key phrase - "30 MINUTE OPERATION"!:doh:

A friend of mine asked me today if this comment about a possible fix was related to the EGT values at specific torque or about the EGT limit implementation.

Made me hesitate

Belsimtek: Were you talking about the EGT limits or the EGT readings being wrong?

Thanks in advance.

PilotMi8 said:

we figured out where we are wrong. We will correct! Thank you for helping!:thumbup:

key phrase - "30 MINUTE OPERATION"!:doh:

Note: While checking out a 1969 copy of the UH-1D/H Operator's Manual, it's apparent the altitude curves in Max Torque Available - "30 MINUTE OPERATION" align with the Normal Power chart in the older manual i.e. 0ft/50 psi = 22° OAT

This sort of makes sense as up to the 610°C altitude curve, torque is the limiting factor, at/above the curve, it's the EGT and a pilot switchs focus i.e. 610-625°C 30 minute max.

TM 55-1520-210-10, 1969 said:

7-46. OPERATIONAL WARNINGS AND CAUTIONS.

Warning
Torque must be monitored as the primary power instrument below engine critical altitude.

The "Military Power" chart from the same 1969 manual, *may* be an estimate for the 625°C altitude curve and might make a valid model for DCS but I can't be certain and would want to validate it against the US Army Aviation Engineering Flight flight tests, as I haven't been able to confirm "Military Power" = "30 MINUTE OPERATION".

Thank you

... who is able to answer the questions that we still have about the engine, we will be grateful for the help (see the attachment).

Unfortunately, the document was difficult to open, so I'll re-post your questions

Questions about the possibility of exceeding the limitations on the engine T53-L-13B

 

We’ve completely remade T53-L-13B engine model. New model is more accurate with precise characteristics according to documents and closer to the real deal. But in the documents we have, it is said that automatic control system has limiter of the max temperature which is not allowing EGT to go higher than 625°! under any conditions. So, it turns out that we cannot go outside of limits. But according to the real pilot's comments on forums it is not true. That is why we want to understand these things:

 

1) Is it possible for a pilot to exceed EGT 625°! and GasProducer of 101,5% by interacting with any helicopter or engine controls:

in AUTO mode

in EMERGENCY mode

during engine Accelerations check (Ground Idle to Maximum) what should be done for exceeding limits?

 

2) If exceeding those limits is possible please tell us about some examples from your or your colleagues experience with details about:

conditions within such exceeding happened: outside air temperature, altitude, takeoff weight;

what was done by pilot with stick, collective, AUTO-EMERGENCY switch or other controls

what were the avionics readings: N1, N2, MainRotor, Torque, EGT ?

 

3) During Autorotation descending: what were the avionics readings (N1, N2, EGT), if Main Rotor rev. is 320-330 (for example – altitude about 3000ft, FAT (OAT)=+15 at Sea Level) ?

 

If there are documents in which such engine characteristics are described or work of automatic control system explained, we would be very interested in getting such documents.

 

Thank you for any help!

Alexander Podvoyskiy, BST, Director

Maybe you should post the questions in a new thread in the main uh-1 forum to get more attention.

Have a family friend who owns a Huey, so have fired across the questions to see if he can help.

We have a current Huey operator in our group. I'll see if he can respond.

Thank you very much for taking the time to make this correct!

it turned out that it was necessary to fix not only the engine, but also the Main Rotor dynamics. Therefore, the process has gone quite deep. We apologize for the wait, but we have to redo engine+Main Rotor performance thoroughly, otherwise we need crutches in modeling, which we really don't like.

Besides, who is able to answer the questions that we still have about the engine, we will be grateful for the help (see the attachment).

I'm a Huey pilot

You are going really deep! I'll try to answer your questions. Let's see.

1) It's possible to exceed those limitations, but in some extraordinary situations.

Exhaust Gas Overtemperature Limits

During starts or accelerations, the following EGT limits must not be exceeded.

a. 625 to 676 C limited duration, 10 seconds

b. 676 to 760 C limited duration, 5 seconds

c. 760 C maximum EGT, do not exceed

You need to have something wrong in your helicopter for these things to happen. Bad FCU, bad compressor. If the above mentioned conditions are met, you need to shut down the aircraft right away in order not to damage the engine.

Gov: i have seen some confusion about this. What GOV does is keep constant rotor RPM at any collective imput. If you lower collective, less fuel is required to keep rotor RPM constant with less angle of attack (less wind resistance). If you raise it, more fuel is needed, so insted of managing the throttle, the FCU does it for you. If you have an axis asigned to your HOTAS or flight controls, you can try this manually for fun. It just isn't.

In some cases, the FCU can fail, for many reasons, so you have the chance of shutting down the RPM GOV and set them manually with the throttle. To do this, you must first go to idle and then turn GOV to emergency. Full open throttle in emergency gov will burn the engine. Unless you have an FCU failure, there's no reason on earth for you to fly without GOV engaged.

2) Any exceeded limitations usually take place in high density altitude enviroments and when maximun available torque condition is met. There's some aerodynamics going on that won't let you brake the aircraft mechanically. You will loose rotor RPM and fall before overtorquing for example. Depending on OAT, aircraft weight, temperature, you will have a maximum available torque that when reached will result in loss of power due to engine stall.

What is MAT? Is the maximum available power for the aircraft in specific conditions. This power is read, in the huey, in the Torque gauge. In high altitude density, after going through the performance charts you may come up with a MAT of 45. This means that when you reach 45, you will have reached 101,5% N1 and have a complete loss of power due to the compressor not being able to provide enough air to that power requirement. In different conditions, you may get that 101,5%N1 with a different TQ value.

In this condition of compressor stall you will see a drop in N2/NR with the aircraft going down, TQ is going down also because of power loss, and you will see an increase in N1 (101,5%) and an increase in EGT (because combustion is taking place without enough air)

The blackhawk starts falling and then the pilot, quickly, released the cargo before hitting it. Nice reaction.

In ISA conditions, with light aircraft, you may not have a MAT, and you would be able to reach the mechanical torque, (usually between 50 and 54, depending on engine calibration), which basically means breaking the aircraft mechanically. In this case, because of air conditions, the compressor is able to provide air to reach a power requirement that can damage the aircraft.

3) Autos: I never had an engine out, so all my autos were in a training environment. Closed throttle, all engine instruments (N1, TQ, and EGT) should go to idle values to that air conditions. N2 train is driven by the rotor, so they don't fall completely to idle (4200+/-), but usually stay between 4800 and 5200. THERE'S A CLEAR NEEDLE SEPARATION.

In an engine out i suppose that engine instruments will go to 0. No way for me to know what would happen to N2 in that case.

This is a good source, the maintenance test flight manual. I have one newer (2007) but it's in spanish

https://www.liberatedmanuals.com/TM-55-1520-242-MTF.pdf

PERSONAL OBSERVATIONS OF THE MODULE

I thing the module is pretty good, it gives a really good sensation of flying the Huey. BUT, there are a couple of strange things going on

1) Rotor behaves weird, with a tendency to overspeed really easy, specially when not loaded (no power applied).

2) Engine: all engine parameters are really sensitive and jump up or down when playing with the collective. Example: you are about to start an approach (35 TQ) and you lower collective (intended 25). All engine instruments will go all the way down (10TQ), you will start falling 1500ft/min and then they will go up (25TQ) without raising collective.

Same thing applies the other way. You apply collective, it will jump to a waaaaay higher value and then back to the one it should.

3) Feels TOO maneuverable with speed. Below ETL and in GE feels GREAT.

Hope it helps, let me know if you need more information!

ECV56_Largo

I'm a Huey pilot

 

You are going really deep! I'll try to answer your questions. Let's see.

 

1) It's possible to exceed those limitations, but in some extraordinary situations.

 

Exhaust Gas Overtemperature Limits

 

During starts or accelerations, the following EGT limits must not be exceeded.

 

a. 625 to 676 C limited duration, 10 seconds

b. 676 to 760 C limited duration, 5 seconds

c. 760 C maximum EGT, do not exceed

 

You need to have something wrong in your helicopter for these things to happen. Bad FCU, bad compressor. If the above mentioned conditions are met, you need to shut down the aircraft right away in order not to damage the engine.

 

Gov: i have seen some confusion about this. What GOV does is keep constant rotor RPM at any collective imput. If you lower collective, less fuel is required to keep rotor RPM constant with less angle of attack (less wind resistance). If you raise it, more fuel is needed, so insted of managing the throttle, the FCU does it for you. If you have an axis asigned to your HOTAS or flight controls, you can try this manually for fun. It just isn't.

 

In some cases, the FCU can fail, for many reasons, so you have the chance of shutting down the RPM GOV and set them manually with the throttle. To do this, you must first go to idle and then turn GOV to emergency. Full open throttle in emergency gov will burn the engine. Unless you have an FCU failure, there's no reason on earth for you to fly without GOV engaged.

 

2) Any exceeded limitations usually take place in high density altitude enviroments and when maximun available torque condition is met. There's some aerodynamics going on that won't let you brake the aircraft mechanically. You will loose rotor RPM and fall before overtorquing for example. Depending on OAT, aircraft weight, temperature, you will have a maximum available torque that when reached will result in loss of power due to engine stall.

 

What is MAT? Is the maximum available power for the aircraft in specific conditions. This power is read, in the huey, in the Torque gauge. In high altitude density, after going through the performance charts you may come up with a MAT of 45. This means that when you reach 45, you will have reached 101,5% N1 and have a complete loss of power due to the compressor not being able to provide enough air to that power requirement. In different conditions, you may get that 101,5%N1 with a different TQ value.

 

In this condition of compressor stall you will see a drop in N2/NR with the aircraft going down, TQ is going down also because of power loss, and you will see an increase in N1 (101,5%) and an increase in EGT (because combustion is taking place without enough air)

 

 

The blackhawk starts falling and then the pilot, quickly, released the cargo before hitting it. Nice reaction.

 

In ISA conditions, with light aircraft, you may not have a MAT, and you would be able to reach the mechanical torque, (usually between 50 and 54, depending on engine calibration), which basically means breaking the aircraft mechanically. In this case, because of air conditions, the compressor is able to provide air to reach a power requirement that can damage the aircraft.

 

3) Autos: I never had an engine out, so all my autos were in a training environment. Closed throttle, all engine instruments (N1, TQ, and EGT) should go to idle values to that air conditions. N2 train is driven by the rotor, so they don't fall completely to idle (4200+/-), but usually stay between 4800 and 5200. THERE'S A CLEAR NEEDLE SEPARATION.

 

In an engine out i suppose that engine instruments will go to 0. No way for me to know what would happen to N2 in that case.

 

This is a good source, the maintenance test flight manual. I have one newer (2007) but it's in spanish

 

https://www.liberatedmanuals.com/TM-55-1520-242-MTF.pdf

 

PERSONAL OBSERVATIONS OF THE MODULE

 

I thing the module is pretty good, it gives a really good sensation of flying the Huey. BUT, there are a couple of strange things going on

 

1) Rotor behaves weird, with a tendency to overspeed really easy, specially when not loaded (no power applied).

 

2) Engine: all engine parameters are really sensitive and jump up or down when playing with the collective. Example: you are about to start an approach (35 TQ) and you lower collective (intended 25). All engine instruments will go all the way down (10TQ), you will start falling 1500ft/min and then they will go up (25TQ) without raising collective.

 

Same thing applies the other way. You apply collective, it will jump to a waaaaay higher value and then back to the one it should.

 

3) Feels TOO maneuverable with speed. Below ETL and in GE feels GREAT.

 

Hope it helps, let me know if you need more information!

 

ECV56_Largo

Thanks for the insights

Thanks to everyone’s input in trying to improve the module, I’m looking forward to seeing the results of your work and dedication.

it turned out that it was necessary to fix not only the engine, but also the Main Rotor dynamics. Therefore, the process has gone quite deep. We apologize for the wait, but we have to redo engine+Main Rotor performance thoroughly, otherwise we need crutches in modeling, which we really don't like.

Besides, who is able to answer the questions that we still have about the engine, we will be grateful for the help (see the attachment).

Hey

get a look on the attached maintenance document

TM-55-1520-242-MTF.pdf