Gunnars Driver

No, didnt try it(yet). Som gaming friends try to talk me to get it. What I comment is the statements that really cant be true. For the stick forward ”by a clic on the trim” or mag brake for the same amount, there will be a difference from lateral inputs during forward flight. When accelerating past translational(might be spelled wrong?) lift the rotor will be met by relative wind that increases the lift of the (left) forward moving blade and reduces the lift on the (right) retreating blade. The gyroscopic pressession makes lift come 90 degrees later, making left/forward blade giving more lift straight ahead an retreating blade less lift over tail. This will raise the nose and counter the normal [stick input = rate]. This is the reason why the cyclic will be more forward the faster you fly. In the real helo without stab system you also need to correct for ’statically stable but dynamically unstable” with cyclic to be able to see this( otherwise itll be all over the place).

The Gazelle is a french helo, main totor is rotating clockwise. This means the stick will be needed to displace a bit to the right during forward flight to keep it from rolling left( different displacement in different speeds). This flight test report show this clearly on page 47 ( Lateral control position): https://apps.dtic.mil/dtic/tr/fulltext/u2/a016921.pdf There’s a lot of info about how the sa342 handle, and good data for making a fine flight model or checking the validity of the actual one in this report.

You mean this part of his post ? A helicopter in forward flight is statically stable but dynamically unstable. This means it will not continue in the same attitude if controls are leaved hands of even if trimmed out. There will be a small deviation causing for example nose drop, as speed increases this will raise the nose making the helo climb again and overshoot the original altitude until speed drops and nose drops. This will keep happening with increased amplitude for each time. For a cordinated constand bank turn the stick will be at around the same position as straight and level flight. The helicopter doesnt really ”know” it is banked in a turn. As soon as the stick is moved from centre position( trimmed out for constant attitude) the rotor disc produces a torque on the helicopter causing it to continously roll or pitch up/down untill the stick is recentered again. The idea that a 3cm displacement causes some kind of steady state where the helo stops rolling and continue in a constant bank is wrong. The poster refers to for example the UH-1 in the post. First, the main function is the same as I did described above. But, the rotor system is a teetering rotor system which gives very different caracteristics compared to a fully articulated rotor system like the Gazelle. Besides this the huey has a stabilizer bar ( Bell Hiller) that act as a mechanical gyro and helps stabilising the helo. These two facts makes the UH-1 handle way different than the Gazelle. I havent flown the Gazelle, but I have enough experience of both teetering rotors, fully articulated and rigid rotors to be sure abut this. I havent bought the DCS Gazelle(yet), but are looking into this meanwhile I wait for the Bo105 module, thats why Im following the threads. [Edit]I googled to find info from R.Prouty(I got all his books, supplied by my work). He is a very well seen expert in helicopter aerodynamics. Very few people, if any, question hes knowledge. https://books.google.se/books?id=rxryAgAAQBAJ&pg=PA100&lpg=PA100&dq=uh-1+bell+hiller+stabilisation+bar&source=bl&ots=p-CenpwkZg&sig=ACfU3U22zSvuyjeTfjb6L_k44vXBU8gizw&hl=sv&sa=X&ved=2ahUKEwjs5-DGnqjgAhVFDiwKHReCAOgQ6AEwEnoECAQQAQ#v=onepage&q=uh-1%20bell%20hiller%20stabilisation%20bar&f=false Ouch, long link. If interrested, read s.77.

Yes, that normal, on all helos. If you move the stick for example to the right it will continue to roll untill the stick is recentered. Moving the stick right causes the blades angles to induce a rolling moment to the helicopter. This doesnt dissapear until the stick is centered. Depending on the main rotor direction you will have the stick slightly to the left or right during level flight, and about the same position in a steady turn.

I dont have the Gazelle(yet). Looking around a bit, but heard from friends and read about the flight dynamics. Anyway, about: That like it is to fly real helos without a stab system. Specially the more ’agility’ types. Most of those helos, even if trimmed to perfection when you release the cyclic it will start to deviate within one or two seconds. Trim is not like for the aircraft, to make it possible to release control for a longer period. Its for neutralizing the stick force, so the pilot arm does’nt need to fight the forces. The B206 and huey with teetering rotors are a bit more forgiving, but then: they aint the most agil’ helos in the block.

The only practical solution in cockpit is to look under the goggles when looking inside. The refocus thing is technical possible but it isnt really possible to do this during flight - you set the focus before flight at around ’infinite’. This is the only way to do it and to do it safe. I got around 20yrs of NVG Flight and one if my main tasks is instructing other pilots/crews on NVG Flight. Never adjusted focus for inside, and never heard of before. The time to re-set focus outside would be to long and you cant really guarante that the setting is perfect after each time. Besides this, the human eye is a lot better than NVG when getting sufficient light levels, wich you have no problem achieving in a NVG Compatible cockpit. All lighting is selected not to be in the wavelength that NVG are sensitive for(actually the goggles have filters, ”minus blue filters” to allow for either green only lights, warning panels with green/yellow/red warnings or for full 4 colour displays. For the cabin crew I /We teach the possibility to adjust the focus closer, to have the close vicinity sharp when doing landings in small clearings. On trick I teach is for the cabin crew to test one eye focus closer to see threes and underneath the helo and the other eye/tube a bit further or infinity. Not every one can cope with this so in the end its a personal choise how to set them or readjust during flight.

Nice work ! :thumbup: I think at least the Swedish Bo105 had a bit different look on the uppermost part around the lifting loop for the rotor head. There was a "glass" (well, see-through part anyway, probably plastic...) around the sides, so you could check the oil level in the rotor head. Maybe an extra equipment not installed on all Bo's ? Edit, googled.

Is the jack stall( servo transparency) modelled in the Gazelle?

The low altitude rolls are not looking like how it would be possible to manouver the real Gazelle. Not even if dumping the collective to the floor during the roll( which you normally do to make the roll look anything like a roll). To not loose altitude on a roll you need to do that, and also push the cyclic forward to get the main rotor to produce some minus G. Both type of manouver can be seen in different displays with the Bo105 on the 'tube. Collective dump only, the height loss in a roll is easy to notice.It may be encountered by a good amount of positive climb before the roll but the helo will loose altitude during the roll. Collective dump and nose pushover to -G can make the roll quite straight. IRL I'd say that would take some practise to perform pretty. I had the rotor head pointing down a few times with the BO105. :megalol:

You might wanna google [gyroscopic precession]. If you loss lift on retreating blade perpendicular to the helo nose direction, the resulting lost lift comes in action 90 degree later in the rotor rotation. Steering input is faced 90 degree before the desired action to counter the gyroscopic precession. If you like to roll right with the Gazelle, and move the cyclic to the right the blades will increase the blade angle straight back/over the tail boom, and decrease the blade angle straight forward.

Certification of helicopters call that VNE is marked not higher than 0.9 x the safe demonstrated indicated airspeed. IRL you won’t get into problems until at least a higher speed than 1.11xVNE. I didnt read the module manual but due to the gyroscopic precession the retreating blade stall should mainly make the nose go up. Theres a lot of argument in other places about right roll or nose up, so we might not go there. Also, not all helos VNE is due to retreating blade stall. Some have other issues like bending forces on the rotor mast and so on. There is also the possybillity to stall the main rotor ( or part of) by G forces. This behaviour is closely related to retreating blade stall ( easiest to enconter in higher speeds) and at least in the Bo105 it gives a clean nose up( actually not really nose up but tail down due to lost lift).

Did you try the Huey or DCS with VR ? When you can, you must have. Its that big difference!

[FBV][/FBV] Ja, det är en ’bugger’ med glasögon i det fallet. Far North, hur långt upp? Luleå i mitt fall :-)

Thats right. Very nice job so I havent had any plans to leave. A licence maybe useful after retirement. (I actually have licence for fixed wing)

For the flight model I think its very nice, but it isnt perfect. I think the input lag that teetering rotors gives isnt really there. The slow response, yes, but the delay isnt really there ? I was not type rated on UH-1 but I have a few hours in it. I flew B206 during basic traning. I know getting back to the B206 and the flights in UH-1 really took some concentration when the spinal behaviour was the Bo105 control physics. I expected the same in DCS, but it doesnt happen. Anyway, I enjoy playing around with the DCS Huey. Its a very good flight model even if it are differences to the reality. The 1:1 to reality isnt important to me, and I actually flown some FFS simulators that was way worse than DCS UH-1 ????

I think its quite easy to fall in that trap. Ive got > 5k hrs. No licence.

Its because of two factors: 1) The Engine power model is off. Engine cannot produce the power it should without the EGT getting to high. In real life this would detoriate your engine if you did fly with to high EGT. How much and when, we really dont know. The model seems to be quite ok in that perspective. This means you can’t use the performance charts and you can not fly the helo as heavy as it should be possible to do. 2) The engine catching fire is because of the engine damage model. This is not right either, because a helicopter turbine engine doesnt catch fire dou to flying with to high EGT. It would detoriate depending of how much over the EGT limit it could be anything between ’Expensive overhaul when doing normal service’ to ’engine break down in flight’. But it wouldnt catch fire. Turbine engines typiccaly catches fire when a fuel line breaks or the oil system starts leaking. I dont know if they know this and will fix this also. Anyway, fixing 1) will make 2) become a non factor when flying inside the limits.

Spot On ! For the selection tests for (at least) Swedish Airforce, there was a stick and rudder jigg for coordination tests when I did it a long time ago. Once got to test the newer version and they told me they had needed to make the test harder due to lot of people beeing better at it from conputer training. They actually had put in something that could be seen as deadzones. It wasnt as easy as before ! I think the main fix is to make the potentiometers work fine, and use as little deadzone as possible. The best fix, as you say, hall sensors. Im in the work of making own pedals, and will use hall sensors( same type actually )

No moving part but some INS/IRS systems measures the eart rotation to find the latitude by it self. For this the A/C needs to be stationary. All INS/ IRS has to perform an alignment after the INS/IRS is powered on. For this the land based way is to measure earth rotation etc. This cant be done on a moving ship the regular way, because the A/C moves (position, course, roll and pitch) changes during this face. Some A/C can still perform this task by themself, witouth connection to the ship, but not all. [Edit]I can add that the own-system-alignment takes longer time on a moving ship, so the connection to the ship, getting information should shorten the alignment phaze on ship operations. So thats the reason for feeding the aircraft from the ship. Also, GPS is not OK in war machines as the only navigation source. A GPS boots with good precision in no time, but is dependent on a external signal that can be disturbed or spoofed. INS/IRS is not sensotive to this, but need to align properly to be accurate enough for modern warfare.

Discussing the photon having mass or not might be considered a slight thread drift from ”Why does mach 1 only read 1270 kph” :) Most common explanation to black holes is that gravity is so strong that even the light cant overcome it.

Yes, my "only" was refering to almost every post earlier in the thread stating that the speed of sound is dependent of air density and temperature - which it does'nt, only the temperature. I also knew about the humidity, but thought that a white lie would make things easy for the regular DCS-player - which it didnt. :doh: For the regular DCS:er, check the excellent picture in post #12. It is easy to se the 100% relationship between temperature and speed of sound. The same temperature simply give the same speed of sound. At sea level and +40 c you have your 1% difference between 0 and 100% humidity. The bigger difference comes from the warmer air containing a lot more water than normal temperatures. Most cases, the highest temperatures give low humidity in air, so +50 and very high humidity is rare, except for in the rain forrests. But I guess not many people travel in high mach numbers in the djungle. :)

1) You couldnt handle such amounts. 2) Less than 1% stated, for a quick understanding for the average DCS:er. Try use a calculator to see the difference at, for example the air pressure 200hPa/mbar, put in 20kPa. ( it correlates to roughly 39000 feet, so you are in the tropopaus. Use -56.5 degrees C. 0% humidity gives a speed of sound of 295.65 m/s. Then change to 100% humidity. Now you are up at 295.66 m/s. Thats 0.0034%. You might be able to handle those percentage actually.

But the difference is so small that the normal DCS:er can disregard your post. Between 0 and 100 % humidity in air the sound of speed changes less than 1%.

Speed of sound is only dependent on temperature in air, not pressure.

For 1) I havent tried slingload in DCS but in real life the load determins the possible speed. A really heavy but small volume load can in almost every case be flown to the maximum slingload speed. Lighter loads with more volume or area or those with stuff causing aerodynamic effects may sometimes limit the max possible( or max comfortable) speed to very low numbers. Was the slingload the same? If it was the same, PIO might be the case. A 30 degree banked turn should recenter the load. If the speed is t to high for the losd it should fly well after the turn.