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PeterR

Question re: Bjorn's MD500D

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When flying in the 500D, the craft likes to take off backwards when you leave the ground. Upon inspection from the outside, when the helo is on the ground, the plane of the main rotor is tilted back quite a bit. Only when pushing the cyclic full forward does it lie parallel to the ground *. Is this normal (i.e. does a real 500 require lots of forward cyclic to take off into a hover)? I didn't notice this tilt in some photos I have of the 500D. Could it be due to the orientation of the rotor itself or the angle of the skids? If it's the rotor, does anyone know how to adjust it?* The model doesn't take into account precession so disregard that detail in the rotor tilt/orientation. As Bjorn said, "This aircraft is depicted as an artist's presentation only."

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It appears to me that this is due to the skid angle, though I don't know if this is accurately modeled. In reviewing my instant replays, I tilt forward a bit to enter and maintain a stationary hovor, and the fronts of the skids are the last point to leave the ground.This by no means takes full forward cyclic for me. How do you have your sensitivity/deadband set?

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My sensitivity is max with zero deadzone. I was only looking at the external view of the helo with skids fully on the ground when moving the rotor to a position parallel with the ground, not actually hovering. When you're off the ground, I agree that it doesn't take full forward cyclic.So, if it's the skids, then that means that I need to learn Gmax to fix it. I seem to recall that there was a float version of his helo? Does it also tilt back? I don't want to fix the wrong thing :-)

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Well, I'm gonna take a guess here about this rotor buisness:It seems to me that the MD500 is generally a fast helicopter. For a helicopter to move horizontally, the rotor disc must be tilted in the desired direction....in this case, forward. The faster you want to go in this (or any) direction, you must tilt the rotor disk at a greater angle into the desired direction. If the MD500 would sit perfectly flat on the ground, the cabin would have an uncomfortable downward angle during cruise, since this is a relatively fast helicopter. The problem with the FS model of this helicopter, is that the rotor disc is not aligned with the horizon when it sits on the ground...in stead, it is aligned with the helicopter, wich is leaning back slightly due to the skids, and this is to minimise the down angle of the cabin during cruise. SO, all we need is someone who knows a thing or 2 about .air files to adjust the static angle of the rotor disc, and we will be in buisness!Max

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I found a photo of the military version of this thing and its skids were definitely shorter in the rear. So I suspect you've got the right idea, Max. The rotor needs to be realigned. I remember seeing an air file tool on simviation. I'll have to check it out.

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Max,Unfotunately, the plane of the main rotor is not a function of the .air file -- it is strictly in how it was built by the author.In the past 2 years, there has been ONLY ONE helicopter of the "tilted-forward-rotor" variety that has been correctly built for FS. That is Shlomo Hakim's CH53IAF (there's a US Navy repaint available).To give you an idea of what I mean, have a look at this http://members.shaw.ca/cbooth/helihover.htmCalhover long and prosper

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yes, i'm aware.......but we are discussing the flight model only. The visuel model is fantastic as is, in my opinion.

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Perhaps you misread -- the "static angle", or any other angle of plane of main rotor CANNOT be adjust through the .air file. The images I directed you to are to illustrate they are always at a FIXED angle in relation to the rest of the aircraft.If you are STILL convinced it can be "fixed" by an .air file expert, so be it. Good luck.Calhover long and prosper

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Cal,Does the CH53IAF model with the tilted rotor tend to go forward when you first lift off? Since its rotor is tilted forward, I would guess so. The 500D model tends to go backwards at lift off because the rotor tilts back (relative to the ground, not the body) due to the angle of the skids. Once the 500D is in a hover, the body pitch seems correct (front of skids lower than rear; see photo below) or maybe the photo is misleading with regard to the pitch of the skids.

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The 500 in the back shows its rotor tilted well forward..... :-outta Francois :-wave________________________Francois A. "Navman" DumasAssociate Editor &Forums AdministratorAVSIM Online!email: fdumas@avsim.com________________________

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Francois,Yes, if the CH53IAF is lifted off in the same attitude as it sits on the ground, it will most certainly go forward. Lifting off into a hover requires proper piloting technique. The nose wheel must be lifted off first and when the hovering attitude is attained, a touch more power will bring you up into a 3-5 ft hover.As for the OH-6 images -- I find them both inconclusive. The one in the background has the rotor stopped. Only the forward blades are visible and I think the blade droop creates the illusion it is tilted forward. The aircraft in foreground appears to me to be just beginning forward flight which would account for the slight forward tilt of the skids but there's really no way to tell for certain. The kind if images we need are difficult to find.Calhover long and prosper

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The kind if images we need are difficult to find.You can say that again, Cal. I've been looking at many, many images. The ultimate solutions are (1) a video or (2) an OH-6/MD500 pilot.

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Hi allConcerning the MD500 (or 520/530 whatever...), when the rotorhead stands neutral, it's tilted slightly forward. The Fs model does have it's rotorhead horizontal towards the ground.....hence the backward flying, as due to the skids, on the ground, the -500 stands slightly nose up. (guess the only serious flaw of Bjorn's splendid model)Wishes,Shoshana :-smile12

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Hi Shoshana !!! How are you doing down there !!?? Having fun I hope :-)I have been trying the 500 all evening now... got some screenshots this time too ...LOL!! Don't know if I'll share them here .... :-roll :-roll It definitely ALWAYS flies backwards when taking off.... unless you push the stick forward... but then it's difficult to gauge 'how much' ! :-( I am not a good pilot yet..... glad I know more about making pictures ...;-) :-outta Francois :-wave[table border=0 cellpadding=10 cellspacing=0][tr][td valign=bottom" align="center]"At home in the wild"[/td][td valign=bottom" align="center][link:avsim.com/alaska/alaska_051.htm|Don's Alaskan Bush Charters]"Beavers Lead the Way"[/td][td valign=bottom" align="center][link:www.avsim.com/vfr_center/mainpages/vfr_flights_main_page.htm]VFR Flight Center]"Looking Good Outside"[/td][/tr][tr][td valign=top" align="center]http://avsim.com/hangar/air/bfu/logo70.gif[/td][td valign="top" align="left" colspan=2]http://ftp.avsim.com/dcforum/User_files/3cc3af591d0ea72a.gif[/td][tr][/table]________________________Francois A. "Navman" DumasAssociate Editor &Forums AdministratorAVSIM Online![/bemail: fdumas@avsim.com________________________

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It does indeed seem to sit pretty much 'backwards' and that rotor is almost horizontal I would say.... :-outta Francois :-wave________________________Francois A. "Navman" DumasAssociate Editor &Forums AdministratorAVSIM Online!email: fdumas@avsim.com________________________

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Thanks, Cal. Yep, those photos pretty much show that the rotor and skids are at the same pitch. So, now I just need to know how to fix the .mdl file to pitch the rotor forward a little.Hi Shoshana! Good to see you. Hope you'll be popping in some more.

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Fortunately, you can't "adjust" the .mdl file -- the original author (Bjorn) would have to make change to the original source file and recompile the .mdl.I say fortunately because I'm sure it doesn't take much imagination to realize what would happen if people could easily modify .mdl's.Calhover long and prosper

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Hi Francois,All is well here, I'm having a really good time here I tell ya!!And being a BFU'er myself......I saw the pics....really cool!!!. The backward flying of Bjorn's model has been noticed by many, and as I had said before, it's the main flaw of the model, as the rotorhead should have been aligned with the chopper's CG, not to the skids, but hey.....maybe Bjorn will fix that in the near future...I surely do hope so for all the "chopper-jocks" !!! Wishes,Shoshana :-smile12

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I didn't know lots of other were talking about the rotor. I was just trying to understand what was happening. It's the engineer in me :-)Yeah, I hope he'll be able to adjust it. It's a great helo. I wonder if I should write him. Maybe he gets too much email about it already?

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BFU/Hughes 500D Pilots....I have made a few modifications to the Distributed Weight and Flight Dynamics with the kind approval of Bjorn Buchner, the main changes are as follows:1. Aircraft Specifications ammended within AIR file to represent a more accurate flight model (original used Bell 206 data):-2 Dihedral - changed to help compensate for coning.3. Engine power output increased to better reflect H500 characteristics.4. Aircraft Gross weight reduced to reflect Hughes (fuel/passenger) 5 Pilots weight (165lb) CFG longitudal offset corrected.6. Distributed weight more characteristic of the 500.7. Hovering is now more realistic.The resultant changes should now provide a more accurate flight model with a very slight forward attitude during transational lift. I feel this now compensates for the slightly-forward tilt of the rotor blades (designed on the model) during lift. At first - I overexceeded weight distribution and the aircraft had too much forward attitude during lift!Known Problems: Roll Dampening still needs some minor work, Engine performance characteristics do not 'accurately' translate in FS2002. I flew the 500D around Chicago and she handles beautifully, flares great and hovers like a Bee!Anyway - try the files and let me know if you like them!For convenience, I uploaded to one of my old CFS sites - here is the link, just go down the page to LINKS and you will see them!Backup your original hughes500.air and aircraft.cfg files in your main BFU500D aircraft folder and rename them to hughes.orig and aircraft.orig and simply paste the two files in place of!http://www.angelfire.com/biz/cqradio/page7.htmlHappy Bush Flying:-rotor

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Thanks Terry!I was looking at the weight stations the other day. Based on the visual model, I came up with the following:station_load.0=0, 1.75, -1.2, 0.8 //Co-pilot (L)station_load.1=165, 1.75, 1.2, 0.8 //Pilot ®This assumes that the CG of the person is in their abdomen below the sternum.I'm curious how you arrived at the 0.300, 0.00, -0.050 location for the load.

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Peter,Yes, at first, interestingly, it would appear that the pilot CG should be placed at a logical longitudinal point (based on the visual model - as you suggest) from the SDK's suggested reference datum. I tried this and it resulted in a 'dramatic' low-nose attitude! Then I realized that the SDK reference datums were, of course, all based upon fixed-wing flight-models and the difficult task was how to easily interpret MS SDK as applied to rotory-wing and the very precise CG extending down below the mast - By simply adding weight to the suggested 'stations' therefore wouldnt work in this (Hughes) example - because, if you added the weight of 2 people (eg 330lb) where logically the SDK suggests the stations should be, the amount of cyclic necessary to overcome the uneven CG would be totally out of limits!As a result of this excercise, I arrived at the figures shown, and this seemed to work out fine!... Of course, having said all that - we as helo-flight-modellers, are conflicting to some degree with MS original aircraft-container, which (as the default) sets the 206B realism-scalar to a minimum, and this sets the 'general scene' - which 'technically' is supposed to make the helicopter easier to fly.... in actual fact, the more realistic we make our model - by changing FD values - the harder it 'technically' would become to fly, so 'go figure!' :-hmmmI mention this because the 'original Hughes air file' is (like many helicopters) was based upon the 206B flight dynamics - which, in turn was based on earlier FS fixed-wing air files - With the recent phased introduction of the SDK's we are in a much better position now to adjust the flight dynamics and aircraft models to be more representative of the real thing - So, do we want the real thing???The 3-D modellers - like Bjorn who produce such excellent visual models (as the H500D could (if they so desire) now offer to leave the fine-tuning of the helicopter FD up to the individual's flying-application for the particular helicopter?Anyway, I now have the beautiful Hughes 500D engine warmed up and I think I want to go picnic on a nice Bahamian beach :)Happy Flying:-rotor

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...For better convenience - I have also uploaded the files (Hughes 500D.zip) to Frank's site and it should show up on there in the next day or so.... I will then REMOVE them from my OLD CFS SITE.

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