Gunnars Driver

I’m sure it will be the NH90. - We will have to wait forever :-) - It will be the most expensive module so far :-) But it will fly like a dream.

From FM: https://s7.postimg.cc/820csp9mj/UH1_CGlimits.png https://s7.postimg.cc/r5to92p1n/UH1_CG2.png

Yes. The CG limits usually is in front of the rotor mast. Stability in forward flight comes from balancing forces against each other. CG in front of rotor mast and stabilisator on tail boom gives a downward force in forward flight. This is mainly the same principle as an normal stable fixed wing aircraft also. For the UH1, the longitudinal cg limits is 130-144 inch rear of reference datum. Rotor mast is at 133.5 inches at the top, but is 5 degree tilted forward, making the longitudinal limits to be situated forward of the rotor mast shaft on the floor. [Edit]Of course a typo did sneak in, the CG limits is 130-144(corrected above from typo, 140-144) [Edit]Before getting shot down by anyone, when I say CG limits usually is in front of the rotor mast, this is a simplification of reality. But just to make it easy to understand. If I remember it correct the UH60 has the mast in front of the CG limits, and the last two helos i did fly and still fly has the rotor mast around the middle of the CG limited area. ( I sell CG calculation apps at app store, so I have at least some knowledge about it, http://sevenbytes.se/ )

Egt, BC, EGT :thumbup:

EGT. Exhaust Gas Temperature. EGR: Exhaust Gas Recirculation, emission control systems in automobiles. :)

- Barometric gives [Altitude] = Height above the set pressure for mean sea level/QNH, or flight level, or height above runway, QFE. - Radar alt gives [Height] = Actual height between helo and ground at present position. Barometric is very good for separation between aircrafts. Set the same QNH or QFE or use 1013,25hpa /29.92 in the Hg and you can avoid each other by selecting different altitude. Barometric is very good for separation to ground. Plan your flight and calculate the altitude needed to clear obstacles with sufficient margin. Radar alt is a very good complement, and for certain procedures its good. But it only tell you the vertical measurement, meaning you have no clue for the margin that's ahead. You cannot use it to avoid a high steep mountain with higher vertical size then the radalt max value.

Yep. The gyroscopic precession makes the action from a input 90 degree later in rotation, that might be the confusing thing for people trying to get this? Rolling left ( cyclic stick perpendicular to the left) will make no change in pitch on blade when straigh to the right and straight to the left. Maximum pitch increase will be when the blade are pointing straight back and maximum decrease in pitch will be when blade is forward. When rolling left the left blade moving down gets higher AoA relative to air, thus higher lift and gyroscopic precession makes this action come 90 degrees later, increasing lift behind rotor mast= nose down. Right blade going up see decreased AoA = decreased lift and action fomes 90 degrees later, nose down. All this is a bit theoreticall. IRL you doesnt notice this. Roll rate vs blade speed make the nose up and down so small so you dont notice this fenomen.

I’d say that the large collective/ much power will not help when helo already is in developed VRS. It is probably/maybe possible if descending but before VRS is fully developed, but it probably depends on how early you increase collective(= before entering VRS). The vortex ring recirculation of air causes the angle of attack on the blades to decrease. This causes lower lift, and increased rate of descent, still high blade angle( but low AoA) makes the power demand high without producing lift. Increasing collective causes a faster recirculation of air, and still low AoA= low lift. It os not possible to outfly VRS with power. Ill back this up with this: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20060024029.pdf ( ”Model for vortex ring state inluence on rotorflight dynamics”) I also have the complete series of R.W Proutys helicopter aerodynamics books. Got them at work, and I think he is a king on the subject, and he is aknowledged by all helo pilots I know. I dont know if the books can be found online, but some articles for magazines on these subjects is found on the net. I’d say that if we find some difference between sources, R.W Prouty should be seen as the spurce of facts. For example, the US army statement in post above is directly contradicted by US Navy NATOPS: ”The only solution for Fully developed VRS is to enter autorotation to break the vortex ring and when cyclic authority is regained increase forward speed.” Digging to deep into this subject will make this a neverending thread. Threads like this already exists in IRL helo pilot forums. Also, Opening the discussion about VRS vs ”settling with power” will also make it last forever. Even different governments and avitation auhoritys cant get along so....

The conditions to get into VRS differs from the conditions experienced when in a fully dveloped vortex ring state. To enter, you need enough power and rate of descend that cannot be too high( you need power applied). When in a developed VRS, increased power/ collective causes higher rate of descent and maximum rate of descend inside VRS can be high. Looked at the video, but only in ipad and i think it was hard to actually see if it was as a IRL VRS. To short time, and to small clocks... I’ll test how the module behaves the next time fly the huey module.

If your question was refering to my post, see your first post: if you reduce the collective untill -2000 to -3000 fpm you should be autorotating. With too little power applied there will not be a vortex ring developed, because you are descending faster than the downdraft air produced by the rotor. If encountering VRS at good height, you can escape by simply lovering the collective to autorotative state. I do not read your second post as being in the same state as the first. The second post, yes that sounds like VRS. Most books ( and probably google searches) give a very broad band for when you are in danger of VRS. That’s because the theory must include all types of helos. ( And maybe a bit of not getting sued by someone that got into VRS outside the given values.) Higher disc load( more helo weight per rotor area) means downdraft has higher velocity and this mean you will need to descend faster to get ibto the dangerous area. Lower disc load leans risk comes earlier at smaller rate of descent. A Robinson R22 will be in danger at a much lower rate of descent then a CH53. It is possible to calculate the theoretical rate of descent for each helicopter type. We got the numbers for all our AF helo types after we had one crash due to VRS some 15 year ago.

Nope ! IRL, no helo can outpower VRS. I dont know for the DCS-module, never tested how the VRS is simulated. You don't outpower it, because the air is recirculating and more power only increases the rate of recirculation, and the sink rate. First of all, Id say you have way to high rate of descent to get into VRS. The rate of descent must match the helos downdraft speed and helos with lower discload has lower downdraft and also reach VRS at lower vertical velocity. The Huey hasn't that much of discload. You need to be in the dangerous zone of sink rate but not to much sink rate, because you need your rotor to produce downdraft so the vortex ring can develope. Id guess you should try around 750fpm(just a rough guess based on disc load and comparing to other helos. Higher weight means you need a little more sin rate to catch the downdraft, because you are sending air down faster the heavier you are), and if or when you feel that the sink rate increases if you increase power, then you are there. IRL there also is increased vibrations and nose wont stat exactly still due to the tail rotor meeting disturbed air - I dont know if all these signs are modelled in DCS. If in a VRS, you should be able to use full power and the sink rate just increases. In real life its not that easy the hit the sweet spot and enter a real VRS. What you described looks more like in real life not hitting the right position to stay exactly in the bad air. Do you set the winds at altitude to zero ? If at high altitude, how can you be sure of hover exactly still, not moving at all ? I know that IRL it can take qiute some try's to find the "non sweet spot".

Yes, and those limits are not currently marked correct on the EGT-meter. We hope they’ll fix it as well, so people just can look at the EGT-meter and stay below the appropriate red line. Stressing it out, just to be sure BST notice it.

And we also hope they’ve learned that overtemp the EGT doesnt start an engine fire. Hot section of turbine is built to stand heat and has no combustionable parts. Engine fire is when a fire starts inside the engine compartment but outside the engine hot section. Engine fire sensors check for fires in engine compartment, most probable fuel leak that caught fire, or possible oil leak caught fire. You can overtemp an turbine engine so the turbine blades leaves via the exhaust without causing engine fire.( Ive seen this IRL). You maybe could have and engine fire after an uncontained engine failure, but then there has to be a big bang first and the engine would break down, immediatly stop producing power. Most cases this should come from an massive engine overspeed, gov fail and broken drive shaft at the same time, or something like it.

If you are flying own missions you could try to lower the OAT( temperature) so the EGT can stay inside the limits. I havent tried it but if you set OAT to -30 C or so this hopefully give you a margin to be able to carry load. This to make you able to fly as before, maybe your load and flying style isnt even close to real world but you at least can continue. I think there is a lot of DCS pilots that lacks of understanding how a helicopter should be operated and this will continue to produce threads like this even when the performance is trimmed to really work as IRL. One part needed to the manual is ”basic helicopter performance understanding” and ”Do and dont’s”. Written in a easy understandable way, BST and we only need to refer or link to this part of the BST manual instead of trying to explain it over and over again. I only briefly flew the DCS UH-1 to MTOW, but Ive tested a bit due to the threads around. Without specially trying to break the engine, it newer happend for me( kept the EGT within limits). If you keep EGT within limits, the engine stays with you the whole flight. I tried overtemp the engine and I actually flew big traffic patterns with the collective stick under the armpit until the engine broke.. Very bad abuse and the engine didnt break until after the complete circuit( 2 minutes?) I think IRL it had been a fat chance not being able to complete the circuit. Of course newer tried it IRL but it is a such big no-no that its actually a good thing that DCS/BST takes the engine away from such unresponsible pilots. Tested autorotation by shutting the engine and after that knowing the autorotation works fine, I by purpose used to much power( high EGT)and the engine broke down. I was able to autorotate every time, even from low level. I found that the cyclic stick was much less responsive when entering an auto than IRL. This makes it harder but still possible. In some special situations you cant survive in DCS when you should live through it IRL. For mast bumping, it newer happend to me until I read complaints in threads and tried to develop it. My findings was that it feels like it happens only when you are doing the big no-no’s. IRL its easy to feel when you are producing low G, and stay safe. In the sim low G cant be felt so you need to know how your stick management affects G. Still, if you fly like a real helo pilot was learned to fly a teetering rotor helo, it just wont happen. To others, a syntetic ”G-meter”, perhaps close to the red stick position graf could help learning to stay alive. I think there is some EGT tuning needed för BST but otherwise I understand that DCS should be as much ”simulator” as possible and with this close to IRL. If this is the philosophy DCS pilots will fall in to the traps of how to fly a real helicopter until they learned how to do it.

Per definition the yaw should be the other way on Mi-8 because the rotor turns the opposite way. Thats right: in final part of landing you shall not fly the ball centered. Instead you shall align the helo with the landing direction. This is important( IRL) if you loose your engine, so your land with the skids parallell to the ground and can glide on them. Failure to tho this can cause the helo to flip over instead of gliding. Also, any wind from either side will cause the helo to lean L/R meaning in hover you cant center the ball. Also, actual center of gravity causes the helo to lean right or left, specially noticed on a teetering rotor like UH-1 has.

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...

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.

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 :-)

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.

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

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.

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" :-)

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.

Talking about wind - this thread is drifting. I didnt read all posts, some are talking about the same thing but with different views. YAW = Angular movement around the vertical axis. I have > 5K h on different helos, and quite some time on full flight sims(FFS). I have not felt any beaviour on the DCS UH-1 that is very of, taking in count that the Full flight sims may cost 20.000.000+ Usd/ Euro. Ive flown FFS that behaves not as good as the DCS UH-1... There are some parts you could make better but no biggies. Taking of with a normal take off, performing a traffic pattern and then land again is very close to IRL. The spinal behaviour from real flying works directly on the this module. I would guess that if someone has big problems with the yaw, he either has a bad joystick/yaw pedal setup or lacks understanding of real helicopter flying, or have made some changes to the “pedal trim” or yaw trim or what it is called.

Never noticed any yaw more than normal on the huey. Did a flight just to check, and I didnt see it this time either. ____________\\\ For the real UH-1: Right yaw comes from torque on main rotor. The UH-1H has 30knots as maximum cross wind at hover which means the tail rotor can handle 30 knots plus a margin. ETL speed is around 20 kt. _____________________ In the module, the by me estimated speed( no wind) when the tail rotor not longer can hold the helo square to the wind if taking of sideways seems quite right. I use DCS World open beta, latest version. Have only installed it and adjusted controls, axis and buttons. Not changed any yaw trim settings.