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Holtzauge

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  1. About the prophanging I think the point is that it is possible in the Dr.1, not that it solves all problems. However, it seems the Pfalz is a very different beast in this regard and while Mikael says he is just in the early phases of testing the Pfalz, he did say that his current feeling was that the thin cambered wing profile gives the Pfalz very different flight characteristics from the thick winged Dr.1 and D.VII. When it comes to diving Mikael says he is limited to a ceiling of 2500 ft due to airspace restrictions over the field so difficult to test. About turning characteristics, I will post a paper on that later on when I have updated it. In the meantime you can find the older version over at The Aerodrome forum. Mind you the one posted there right now is a bit dated since it is too optimistic about the Clmax on both aircraft and the propeller model on the Dr.1 needed updating and in the latest version I will post soon the Camel does retain its advantage over the major part of the envelope but the Dr.1 is now actually a shade better at really low altitudes.
  2. Yep, I really like the second low altitude pass! It was priceless standing there when he came back around for that. His D.VII is really is a museum piece but the way Mikael flies it you get transported right back in time to some forward Jasta airfield right behind the trenches..... Some curiosa: If you are wondering about that banging sound the D.VII makes on landing that is just the way it sounded back in WW1: I had a chat yesterday with Mikael and he explained that the wheel axle (steel) is housed in a steel enclosure in the landing gear fairing just as it was back then so no compromises. Everything is as it was in the original and this part of the plane is prone to wear. He said that his theory of why they did it like that was that back then it did not matter: The planes did not in general last long enough for this to become an issue. Another nice detail about the landing gear is that he said to me on an earlier occasion that while he uses bungee-cord for the axle to wheel strut connection, he actually has the original steel springs used by the Germans in WW1 available but prefers the bungee-cord since it has a damping effect which of course is not there if you use springs.
  3. I think Flying Circus is a great simulator and I would love to see a second installment. I think the Pfalz D.VIII would be a nice addition. Below is a link to a video I took last weekend of Mikael Carlson doing test flight number eight in his Pfalz D.VIII. My GoPro is not quite the tool for this but I included the high altitude scene anyway because I just love the whine the plane does when he goes into a descending high speed turn about a minute into the video. Any thoughts on this? Should the Pfalz D.VIII or maybe the Siemens Schukert D.IV be included in Flying Circus? As I understood it from speaking to Mikael, he had the Siemens Halske IIIa engine that was mounted in both aircraft and had to decide which aircraft to build and the choice fell on the Pfalz because apparently there is way more data available on the Pflaz D.VIII than the SS D.IV which would then hint that it would be a good choice also be good for FC. BTW: If someone is wondering where the two posts I made yesterday about Mikael Carlson’s input on WW1 airplane handling characteristics and the Fokker D.VII video I posted have gone they have been moved by the moderators to the free subject section and can be found right under the ”What music do you listen to” thread.
  4. Below is a link to a video I shot of Mikael Carlson putting his DVII through its paces. A video can of course never fully convey the feeling of standing there getting your hair ruffled by a low flying DVII and hearing the Mercedes DIIIaü sing but I hope you enjoy it anyway!
  5. Yep, apparently the Dr.1 can do that and when I asked him what airplane he preferred he actually said the Dr.1 over the D.VII which kind of surprised me since the D.VII has so much more performance but apparently the manouverability of the Dr.1 is so amazing at low speeds that he would take it anyway. Puts MvR fondness for the Dr.1 in a whole new light IMHO. Wait for it: DVII video incoming! Link to video.
  6. I will post a link to a Pfalz D.VIII cockpit walkaround video later where you can see the arrangement. As far as I can tell that is the only detail that differs this from a WW1 example and it looks pretty easy to disconnect if you want a "realistic" FM.
  7. Glad you like it! I can tell you it was just great being there and Mikael is like a walking encyclopedia: He knows these aircraft down to the minutest detail and I learned a lot during my visit.
  8. I recently had the good fortune to interview Mikael Carlson about what it is like to fly his Fokker Dr.1. My initial intention was to include this text in a revised version of a paper I have put together on the Sopwith Camel’s and Fokker Dr.1’s relative turn performance but since the result was pure gold I asked and received Mikael’s consent to post it here as well. Mikael has taken pains to build what is arguably a carbon copy of a Fokker Dr.1 accurate down to the last nuts and bolts. Not only that, but he flies it in advanced manoeuvres as well meaning he is in a unique position to talk about the Dr.1’s flying characteristics since this is not a replica but an actual reincarnation of the plane built and flown as it was in WW1. Mikael’s Dr.1 is also authentic in terms of instrumentation meaning there are no hard numbers on stall and maximum speed available since he flies the plane as it was flown back in WW1, i.e. by feel. Concerning turns, while Mikael says he has not timed them, there is no marked difference in turn times left or right once settled into the turn but the gyroscopic forces do help in establishing a turn to the right while opposing a turn to the left. He also confirmed that the Dr.1 slows down rather quickly in tight turns, just as predicted in my C++ computer simulations. Contrary to common belief, the gyroscopic effect in the Dr.1 is quite manageable and gyroscopic forces are in fact more pronounced in a P-51 according to Mikael who not only flies the Mustang but also the Hangar10 operated Bf 109G-6 putting him in an authoritative position to judge these airplanes relative handling characteristics. Interestingly, another airplane he has flown that exhibits pronounced gyroscopic effects is not a rotary powered plane but surprisingly enough the jet powered de Havilland Vampire with its huge radial compressor. Returning to the Dr.1’s gyroscopic precession characteristics, he said these are quite manageable unless at very low speeds close to stall and that consequently, he tends to lean a loop slightly to one side in order to have control of in which direction the Dr.1 departs should the speed become too low at the top of a loop. The Dr.1’s stall characteristics are very benign according to Mikael and in fact the aircraft does not have a pronounced stall point but kind of mushes when exceeding the stall angle of attack while still retaining good control authority which supports the popular legend that Fokker’s thick winged Göttingen profiled Fokker Dr.1 and D.VII had the ability to hang by the propeller to catch an unwary Entente pilot from below. In yaw the Dr.1 is neutral in directional stability meaning that if the pilot uses rudder to give the plane a certain yaw angle, it will stay there until the pilot actively uses the rudder again to bring it back on track lending credence to the Dr.1’s purported ability to fly sideways while firing its guns. When asked about the Dr.1’s spin characteristics, Mikael said he has chosen not to explore this part of the flight envelope since the high rotational speeds in a spin would cause significant gyroscopic precession loads on the bearings of the engine which seems like a prudent precaution given how scarce and valuable the remaining original WW1-era rotary engines are. A further note of interest is that he said that the aerodynamic overhang balances on the Dr.1’s control surfaces work well and there is no tendency for overbalance within the flight envelope and the aileron stick forces remain light allowing rolling manoeuvres even at higher speeds which is in stark contrast to the aerodynamically unbalanced ailerons on the Pfalz D.VIII which he says are hard to budge at higher speeds. Regarding the Fokker D.VII, he said that this airplane has the same pleasant and well balanced control characteristics as the Dr.1 and in addition has such benign flying characteristics that he likened it to a Piper Cub. Another interesting point regarding aerodynamic characteristics that both the Dr.1 and D.VIII have in common is that they are tail heavy: Given Mikael’s quest for historic accuracy, both planes have been balanced as they flew in WW1 and the center of gravity is as far back as 32 % MAC which explains the significant down elevator needed on the Dr.1 to keep the nose down. In fact, he has equipped his Dr.1 with a bungee-cord connected to the stick so that there is some level of trimming available to handle the stick forces needed to maintain the pronounced stick forward position needed to keep in level flight. With the center of gravity so far back he points out, the aircraft is basically unstable in pitch and needs to be flown preemptively at all times. Taxiing is best done with helpers on the wings assisting in getting the aircraft in the right direction and lined up for take-of. There is however directional control available should it be needed, if the skid is unloaded and the engine gunned to get sufficient airflow over the rudder. Landing the Dr.1 should always be done as close to a three point landing as possible and into the wind using the elevator to push the tail down and get traction for the skid after touchdown. Crosswinds are to be avoided as far as possible and the plane is prone to ground looping and after touchdown some engine power and constant attention with the rudder is needed to maintain course. Attempting wheeler landings is off the table as it is an open invitation for a ground loop and consequently something he avoids doing in the Dr.1. As a final note on handling characteristics, Mikael commented that pilots sometimes like to tell stories and that the Dr.1 is in fact not that difficult to fly as long as you have sufficient experience flying it. Different in the sense that other combinations of control movement are needed but as long as you are familiar with the airplane and the somewhat unorthodox engine control, it is not that much more difficult to handle than a more conventional plane. That however said with the caveat that the Fokker Dr.1 does require the pilot to handle it in the correct way and pay constant attention or, as he puts it, it will turn right back and bite you. I had the opportunity to take some photos as well and below is a picture of one very happy camper (me) in front of Mikael’s Fokker D.VII taken last weekend.
  9. Yes, I had a look at the restoration pictures and it looks real nice! OK, then I get why you need the chase plane. Better get one with a good climb rate then because the 120 hp Dr.1 will as MvR put it "climb like a monkey" But even so, getting a climb time/climb rate histogram to as high as 10,000 ft for a Dr.1 would be great as well! Well when speed is concerned whatever chase plane you choose should be able to keep up though!
  10. Concerning engine power: As I understand it Zach says these old engines can vary a lot in power output which is a bit worry some since it will be difficult to determine which historic figures are the correct ones. Anyway, I guess we can cross that bridge when we come to it: Absolutely fabulous would be to get some solid measured data on climb rates, climb times, turn rates and speeds to begin with and as I understand it the Levil BOM will do just that with good accuracy and that should at least give us a good relative relationship between these numbers for a given power. This would be good I think since with old historic numbers there is no way to be absolutely sure if the climb time figure was with a climb optimized prop and the speed or turn figure with a speed optimized prop or some other combination which could add to the confusion on top of the fact that an engine with a nominal rating could put out a power figure quite different from the rated one. In addition, knowing which of the old historic numbers were done with a reasonable accuracy is also difficult to determine. Doing renewed testing with accurate measuring equipment like you are planning will change all that! I think Zach has a good point about the power you are actually getting on the shaft from your nominal 80 hp Le Rhone and 950 fpm SL climb rate sounds a lot for just 80 hp. BTW: How did you get the 950 fpm number Chill? Do you have a rate of climb indicator installed or is it an average based on a climb time to a certain altitude? About the climb test: I have modeled the Dr.1 with 122 hp and that gives me a 1410 fpm climb rate in the simulations so smack in the middle of your prediction. However, with that kind of SL climb rate that’s a bit faster than your average Cessna or Piper but do you really need a plane to fly alongside? I thought that the Levil BOM would give you that kind of data on its own with good accuracy? Anyway, if you could do a climb test to 3-4 Km that would provide really valuable data since I don’t think either Javier Arango ever did that or Mikael Carlson has either so it would be a first. In addition, really looking forward to the speed/altitude chart since there is so much controversy about the Dr.1’s top speed. Also, good that you plan to do this with the standard 2.62 x 2.3 m propeller which will then make it directly comparable with historic data.
  11. Thanks for doing the testing and posting the results! Must say you hold it quite steady in the stationary turns, especially the one to the right about 30 s in which looked really solid. The ball was in the middle too and as I understand it from a brief chat with Mikael Carlson is that in yaw you really have to chase the Dr.1 since there is basically no direction stability. If you have gotten the Levil BOOM that sounds great since as far as I know it it can give you IAS, TAS and GS meaning you could do a speed/altitude chart. Doing that for a Dr.1 would be great since there seems to be some controversy as to how fast it actually was at SL and I have seen numbers as low as 165 km/h and as high as 180 km/h. In addition, recording a climb time chart would be superb since there are a lot of different numbers floating around on the internet indicating quite different climb times, especially up to 5 Km but I guess that would be really pushing it unless you have oxygen of course. I asked Mikael Carlson about climb tests and unfortunately he was unable to do that due to air space restrictions over his home field. Some questions about your current setup: Do you have a tachometer installed and if so what was the rpm during the stationary turn trial? As I understand it from Zacharias, the Dr.1 standard prop on the 110 hp Le Rhone was 2.62 m in diameter with a 2.3 m pitch (8.6 x 7.55 ft) . What prop do you have on your 80 hp Le Rhone? Another thing I'm curious about is what oil do you use for the 80 hp Le Rhone? Are there good synthetic alternatives available today?
  12. We can always speculate what was going on in Fokker mind. I'm just saying how I think you would look at it from an engineering perspective. I have actually done the structural design of the wing (according to JAR22) on a motorized glider and structural engineering in the tail section on the JAS39 Gripen and we for sure ONLY included what we thought was needed to reach design requirements. I would have been strung up by the privates if the weights department at SAAB found out I tried to put some extra strength in there! Sure the plywood adds as well but mostly in terms of taking the shear load: You need the vertical plywood elements to take shear. It's like the middle part in a steel I-beam: Almost all bending resistance comes from the flanges but you also need the thin middle part to take the shear loads. And sure, the top of the box also adds bending resistance but is primarily there to close the section into a box to take the torsional loads in case of the Dr1 since the wing has no bracing. Aber das war kein herring unvernünftige! : Was ich gesagt habe was spot on and you know it! Sure we don't have any more data points than that single test (which we don't know how it was done or under which circumstances) but we do have the German design rules and sure, 13 g is perfectly possible but is essentially bad engineering when the requirement is 5 because there is no such thing as a free lunch: Added strength means added weight. And then why design for 13 g specifically? Why would he aim for that particular figure? Why not 15 or more? And we are not making anything up in the forum (The 5-6 g ultimate load requirement): Those rules were the design rules set up by the German procurement agency for acquiring scouts for the Luftstreitkräfte in the 1917 to 1918 period.
  13. We'll we could of course apply the same principle to engines: One manufacturer sets a 5 min limit on WEP. I find one tests which shows one engine surviving 10 min so let's use that instead.
  14. I'm going to rain on the parade a bit: First we only have one sample. Second they say 10.7g. OK, so 10.7 g assuming what weight? Did they use a correct base weight or had someone mistankedly used the dry weight and not loaded weight or assumed a too low weight? How did they compensate for some of the weight being in the wing? Did they do that in a right way? How did they distribute the sandbags between the upper and lower wing? How did they distribute the sandbags spanwize to simulate the spanloading? How were they supporting the wing because I don't think they hung it up in the fuselage upside down and if not how did they attach the wing to the test setup? Finally, a built up spar like the D7 probably fails by buckling in the shear web and prediction of buckling is notoriously difficult and the subject for countless masters and doctorial thesis because buckling results are so varying in nature: One sample may buckle at a much higher or lower value than is representative of the average. A bit salty I know but really, unless we know more about this we just have a heresay result for one airplane tested under unknown conditions. However, we DO know that the German design rules 1917/18 stated a 5-6 g ultimate load requirement and you can be sure that that was what Fokker designed for because you don't get extra points for building stronger than needed and building stronger than the requirement just adds unnecessary weight which means poorer performance.
  15. Well the reason the Dr1 beam is so stiff is that it has the 4 spar elements far out from the bending axis where they are held in place by the plywood: Beam theory gives the total resistance to bending as: It= Io + A*L**2 Where Io is the bending resistance of the spar element, A is the cross sectional area and L the distance from the bending axis (in this case the middle of the DR1 spar). Intuitivite one can realize that the bending resistance Io from the spar elements themselves is small: Try taking a h=1.5 x b=5 cm spar and bend it: It will not take much load. (The spar elements own bending resistance is expressed as Io=b*h**3/12 BTW.) So the major contribution comes from the square of the “L” multiplied by the area b*h. So this means that while a built up spar like on the Fokker Dr1 is very strong, it actually derives its strength from the spar elements in the corners. So again, for damage resistance purposes, its perfectly valid comparing the risk to shoot away the 4 x A/4 spar area in a Dr1 with shooting away the concentrated area A in a Camel.
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