entropy@pawl.rpi.edu (Speaker for the Clams) (10/25/89)
From: Speaker for the Clams <entropy@pawl.rpi.edu> I've heard that some early WWI aircraft such as the Fokker DR1 and Sopwith Pup were designed so that the engine was fixed to the propeller shaft and the entire engine spun round and round within the fuselage. The result was that these planes could execute very fast right turns but could only turn left very slowly. Does anyone know for sure if this is true? If so, how fast were the left and right turns, respectively? What tactics were evolved to take advantage of this peculiarity? "He had a gift for quotation, which is a serviceable substitute for wit." Mark-Jason Dominus entropy@pawl.rpi.EDU entropy@rpitsmts (BITnet)
dyson@tut.cis.ohio-state.edu (mark l dyson) (10/26/89)
From: dyson@tut.cis.ohio-state.edu (mark l dyson) In article <10577@cbnews.ATT.COM> entropy@pawl.rpi.edu (Speaker for the Clams) writes: > I've heard that some early WWI aircraft such as the >Fokker DR1 and Sopwith Pup were designed so that the engine >was fixed to the propeller shaft and the entire engine spun >round and round within the fuselage. The result was that >these planes could execute very fast right turns but could >only turn left very slowly. > Does anyone know for sure if this is true? If so, >how fast were the left and right turns, respectively? What >tactics were evolved to take advantage of this >peculiarity? It is very true. The most notable of the aircraft with this engine arrangement were (not limited to) the Nieuport 11, 17, 28; Sopwith Camel; Fokker Dr1; Fokker DVIII; and many more. I don't have the exact performance stats in front of me, but here are some approximations: A Sopwith Camel, flying from 60-80 mph could turn about equally well in either direction. >From 90-110 mph the torque increased to a point where a right turn was possible at as much as 1/2 the diameter of the left. From the mid-100's up to 200+ there was still as much as a 1/3 reduction in turn radius, but the higher momentum of the aircraft would mitigate the torque benefit somewhat. These figures are approximate, but the ratio holds more or less for any of the rotary-engined planes. [mod.note: I meant to mention this yesterday... isn't the correct term "radial", not "rotary" ? My RX-7 has a rotary engine, I thought A/C had radials. Or is a spinning radial also called a rotary ? - Bill ] Tactics for these planes are fairly obvious: if you get into a scissor or circle duel, keep the target on your right, and you get better turn rates. Against a Fokker Dr1, the Camel's advantage was nearly nil, though, as they had almost identical turn rates in all envelopes. The Dr1's forte was its lift, so it had the advantage of making the same turn rates as a Camel opponant, with lower altitude losses per turn. Couple that with the Camel's better dive, though, and the Dr1 wasn't always free to pursue the height advantage. Getting the picture? Almost every plane on the front had some forte' or another. The bottom line was, as always, how well a pilot could react to an enemy's actions, and control the engagement. Why a rotary? In a word, reliability. A rotary could force-feed the lubricant via centripetal force through the center of the engine and up to each cylinder. Carburation was likewise simplified. A stationary crankshaft could be made heavier, and less prone to breakage. One big problem with them was that the throttles were essentially non-adjusting, due to the simplified fuel system. The engine generally self-adjusted to the flying conditions, but tended to stay at a constant rpm at a given altitude. Modifications to airspeed were made with pitch adjustment. I hope this clears up some of your questions. -Mark-
oplinger@ra.crd.ge.com (B. S. Oplinger) (10/27/89)
From: oplinger@ra.crd.ge.com (B. S. Oplinger)
[mod.note: While the first sentence is incorrect, as shown in another
of today's postings, this article does a good job of explaining
all these different engines. - Bill ]
Rotary engines and radial engines are indeed much different. I'll
try to give a much simplified description (as in a wwI aircraft,
in ground vehicles and later airplanes, the fixed part of the
engine may vary) of the differences. A typical engine has a fixed
case which holds the engine parts (block) and looks like (pardon
the ASCII graphics):
cylinders
|| || || ||
\/ \/ \/ \/
________________________ <---- fuel/exhaust on the top here
| | | | |
| ___ | ___ | ___ | ___ |
| |_| | | | | | | | | | |
| | | | | | | | |
| --|-----|- ---|-----|--+-------- shaft (energy provided)
|________________________|
[mod.note: You need a ring job. 8-) - Bill ]
It is broken up into cylinders, each of which has a fuel input
and a piston. The fuel is premixed with oxygen (carburated, hence
a carburator) and pumped into the cylinder. The piston compresses
it and then an ignitor (spark plug) causes it to burn. The
pistons are placed on a shaft in a staggered manner so that as
the gas expands the piston pushes the shaft and other pistons
compress the fuel, it explodes, pushes the piston, etc for a self
repeating cycle. Note: all of the energy is at right angles to
the shaft.
[mod.note: (this is habit forming !) Note that fuel-injected
engines do not pre-mix fuel and air, but inject the fuel directly
into the cylinder. - Bill ]
A radial engine, on the other hand has the shaft fixed and the
piston placed in a star shaped pattern around the shaft (at least
in airplanes) kinda like this:
\ /
\ /
--- o --- the 'o' is the shaft( looking on end)
/ \
/ \
All of the fuel, lubrication, exhaust is based on the natural
tendency of thing to fly outward. The fuel is fed into the center
of the engine. It is then fed into each cylinder and when burnt,
the exhaust gases flow outward. Bolt the propellor onto the
engine block and when the block turns, the propellor turns. If
you think about the mass being moved here you will quickly see
why it was so easy to turn the plane to the left. (Think about
the physics experiment where you stand on a turntable, someone
hands you a spinning bicycle wheel. When you turn the wheel from
horizontal to vertical, the platform turns. Same thing here)
Rotary engines on the other hand, do away with the piston in the
cylinder approach. Instead they use a cam. The simplest
description I can come up with is: Imagine a football. Place it
in a home trash can (you know the round kind with a lid) which
has been cut as tall as the football is round. Now if you turn it
there is a half-moon kinda space on each side of the football and
no space at the points (shink you picture of the diameter of the
trash can if necessary). Now, dent the trash can so that it is no
longer round. The half-moon space will now grow and shrink. At
the point where it is the largest, cut a hole for a fuel
injector. At the point it is the smallest, cut a hole for a
spark plug and an exhaust. If you imagine a bunch of these
stacked on top of each other and a shaft running from top to
bottom, you have a rotary engine. The energy provided by the
expanding gasses is applied more efficiently to the shaft. The
cam turns and so does the shaft, unlike a piston engine where you
must convert up and down to around and around. This should make a
smoother running more efficient engine. In practice, it is
difficult to maintain (as a buddy with a RX-7).
brian
oplinger@crd.ge.com
[mod.note: Wankel rotaries are now being considered for light aircraft,
because of their favorable power-to-weight ratios. Oh, and some
followups may be more appropriate to rec.autos.tech. - Bill ]fiddler@Sun.COM (Steve Hix) (10/28/89)
From: fiddler@Sun.COM (Steve Hix) In article <10577@cbnews.ATT.COM>, entropy@pawl.rpi.edu (Speaker for the Clams) writes: > > > From: Speaker for the Clams <entropy@pawl.rpi.edu> > > I've heard that some early WWI aircraft such as the > Fokker DR1 and Sopwith Pup were designed so that the engine > was fixed to the propeller shaft and the entire engine spun > round and round within the fuselage. The result was that > these planes could execute very fast right turns but could > only turn left very slowly. Rotary (as opposed to radial) engines! Marvels of early post- Victorian engineering. The two most common types of WWI were the Le Rhone and Oberursel (French and German, respectively). The base engines of either make were almost identical, I believe the Oberursel was originally a license-built version of the LeRhone. (Pardon the spellings...) It all had to do with cooling: either you cool with liquid (heavy, increased complexity), or by moving air past the cylinders. You save a lot of weight, at the expense of drag, by arranging the cylinder radially around the crankshaft. Even that wasn't enough, especially in high-powered applications like fighters and observation aircraft. So the rotary was born to squeeze out the last bit of power. (The early LeRhone put out 80hp!) Bolt the prop to the crankcase, bold one end of the crankshaft to the airplane, and let the engine spin: instant cooling wind. Spinning the engine complicated a few things, so they were 2-stroke, and with all that mass whirling about, the planes tended to roll left very quickly, and not so quickly to the right. One drawback was that they couldn't be made to idle easily (if at all), so the pilot had a cutoff switch on the joystick to get power down to manageable levels when landing. Of course, if you cut it off too long or too often, the plugs would foul and the engine would quit. (The sound of briefly cutting out the engine lived on in the movies until long after rotaries had been abandoned by aviation in general.) Another disadvantage stemmed from the 2-stroke nature of the beast...its lubricant. They used high-grade castor oil. Which fumes the pilots would breathe whilst flying. Immediately on landing, the aircrew would leap nimbly out of their kites and rush off...sometime after which they'd report for debriefing. Really. (I thought this was a joke until I got a chance to talk to an old WWI pilot at the Yountville Veterans Home.) ------------ "...I was to learn later in life that we tend to meet any new situation by reorganizing: and a wonderful method it can be for creating the illusion of progress, while producing confusion, inefficiency and demoralization." - Petronius Arbiter, 210 B.C.
cperlebe@encad.Wichita.NCR.COM (Chris Perleberg) (10/28/89)
From: cperlebe@encad.Wichita.NCR.COM (Chris Perleberg) In article <10622@cbnews.ATT.COM> dyson@tut.cis.ohio-state.edu (mark l dyson) writes: > > >From: dyson@tut.cis.ohio-state.edu (mark l dyson) > >In article <10577@cbnews.ATT.COM> entropy@pawl.rpi.edu (Speaker for the Clams) writes: > >> I've heard that some early WWI aircraft such as the >>Fokker DR1 and Sopwith Pup were designed so that the engine >>was fixed to the propeller shaft and the entire engine spun >>round and round within the fuselage. > >[mod.note: I meant to mention this yesterday... isn't the correct > term "radial", not "rotary" ? My RX-7 has a rotary engine, > I thought A/C had radials. Or is a spinning radial also called > a rotary ? - Bill ] > No, the term rotary is correct. There were no radial engines (engines where the prop shaft spun while the engine remained stationary) in the Great War (the 1918 Siemens-Schukert D-VI? may have had a radial -- memory fails me -- but I doubt it). All "round" engines in the First War were rotaries. The last major fighters produced by both the British and Germans in 1918 (the Sopwith Snipe and the Fokker D-VIII) had rotary engines (the French SPAD series had inline engines, as did the Fokker D-VII and SE-5a). Not all aircraft with rotary engines shared the turning characteristics of the Sopwith Camel or Fokker Triplane. In fact, most didn't. The determining factors must have been plane size, engine power, wing-loading and so on (I'm not an aircraft engineer). Some rotaries, like the FE2 or DH2 pushers, gained almost no maneuverability from the engine (they were dogs, in fact). Others, like the Nieuport series and the Sopwith Pup, gained a little, but not much. Other design factors made them maneuverable. The rotary had its disadvantages. First, as engines got bigger and bigger, more and more metal got slung around, reducing efficiency. Second, damage to the prop or engine (like a cylinder breaking off) could unbalance the engine (no kidding), and make the whole aircraft fall apart (extremely unpleasant in the days before parachutes 8-). This was especially a problem in the early days of interrupter gear (the gearing that linked the propeller with the MG trigger so that the MG could fire safely through the prop). Max Immelmann (inventor of the "Immelmann turn") is thought to have shot himself down in 1916 when the interrupter gear on his Fokker E-IV "slipped" a bit and shot his propeller off. Chris Perleberg cperlebe@encad.wichita.ncr.com
krees@zaphod.axion.bt.co.uk (kearton rees) (10/28/89)
From: kearton rees <krees@zaphod.axion.bt.co.uk> >From article <10577@cbnews.ATT.COM>, by entropy@pawl.rpi.edu (Speaker for the Clams): > From: Speaker for the Clams <entropy@pawl.rpi.edu> > > I've heard that some early WWI aircraft such as the > Fokker DR1 and Sopwith Pup were designed so that the engine > was fixed to the propeller shaft and the entire engine spun > round and round within the fuselage. > The result was that > these planes could execute very fast right turns but could > only turn left very slowly. > > Does anyone know for sure if this is true? If so, > how fast were the left and right turns, respectively? What > tactics were evolved to take advantage of this > peculiarity? > Yes, rotating-casing engines were used. I don't know in which planes though. The engine was the Gnome-LeRho^ne, which was a French engine though some were made in Britain by the firm W.H. Allen Ltd of Bedford. (This company is still in business and sould be able to give you more information.) I have no information on the manouverability or specifically developed tactics. Kearton #--------------------------------------------------------------# krees@axion.bt.co.uk British Telecom Research Labs., Martlesham Heath, Ipswich, Suffolk, IP5 7RE United Kingdom. #--------------------------------------------------------------#
djm@castle.ed.ac.uk (D Murphy) (10/30/89)
From: D Murphy <djm@castle.ed.ac.uk> In article <10715@cbnews.ATT.COM> cperlebe@encad.Wichita.NCR.COM (Chris Perleberg) writes: > Sopwith Camel or Fokker Triplane. > >Chris Perleberg >cperlebe@encad.wichita.ncr.com Sopwith also built a triplane (the Sopwith Triplane - wow!) which I saw a photo of in a book once. It looked very similar to the famous Fokker machine. Who copied who ? Murff.....
silber@cs.uiuc.edu (Ami A. Silberman) (10/31/89)
From: "Ami A. Silberman" <silber@cs.uiuc.edu> >Sopwith also built a triplane (the Sopwith Triplane - wow!) which I saw >a photo of in a book once. It looked very similar to the famous Fokker >machine. Who copied who ? Fokker copied Sopwith. As an interesting aside, the Royal Navy used Sopwith Triplanes. (From land bases, of course.) One of their squadrons was an all Black unit, and had at least one ace. ami silberman, janitor of lunacy
cperlebe@encad.Wichita.NCR.COM (Chris Perleberg) (10/31/89)
From: cperlebe@encad.Wichita.NCR.COM (Chris Perleberg) In article <10748@cbnews.ATT.COM> djm@castle.ed.ac.uk (D Murphy) writes: > >In article <10715@cbnews.ATT.COM> cperlebe@encad.Wichita.NCR.COM (Chris Perleberg) writes: >> Sopwith Camel or Fokker Triplane. >> > >>Chris Perleberg > >Sopwith also built a triplane (the Sopwith Triplane - wow!) which I saw >a photo of in a book once. It looked very similar to the famous Fokker >machine. Who copied who ? > Although the Triplane concept was not totally new, Fokker copied it from Sopwith. The Sopwith Tripe was pretty much a Pup with three wings. Like the Pup, it was a good aircraft, and like the Pup, the RFC wasn't interested. The RNAS had a couple of squadrons of Tripes, and in April 1917 (Bloody April to the RFC), Naval 8 helped bail the RFC out. Raymond Collishaw, one of Britian's top aces, flew the Tripe in the famous "Black Flight" -- a group of Triplanes with names like "Black Maria," "Black Death," and "Black Sheep"). The Tripe went up against J.G. 1, Richtofen's outfit, and performed very well. A western front full of Sopwith Triplanes would have changed the air situation greatly. Still, the RFC was looking into the B.E. 12 ... Fokker reacted to J.G. 1's impression of the Sopwith Triplane and came up with the Fokker Dr 1 triplane. The Fokker model wasn't as good as the Sopwith model, having a tendency to shed the upper wing surfaces (i.e., it had a tendency to kill pilots). Richtofen flew the first Dr. 1, while Werner Voss flew #2. Voss was killed in an epic battle against seven S.E. 5as from 56th squadron, RFC (one of the best). Richtofen himself didn't fly the Triplane that much (it was withdrawn for a while so that they could fix the wings), preferring the Albatross D-III. He used at least two Triplanes, only one of which (the one he was killed in) was all red. Chris Perleberg cperlebe@encad.wichita.ncr.com
pvo3366@sapphire.oce.orst.edu (Paul O'Neill) (11/03/89)
From: pvo3366@sapphire.oce.orst.edu (Paul O'Neill) In article <10577@cbnews.ATT.COM> entropy@pawl.rpi.edu (Speaker for the Clams) writes: > >................................. The result was that >these planes could execute very fast right turns but could >only turn left very slowly. > Does anyone know for sure if this is true? ...... >From _Fighter Combat Tactics and Maneuvering_ by Robert L. Shaw: ---------- Torque may also have an effect on turn performance, particularly with high-powered prop fighters at slow speed. The effects of engine torque must generally be offset by rudder power to maintain balanced flight. Normally under these conditions considerable right rudder will be required to balance the torque of a prop turning clockwise (when viewed from behind), and vice versa. Another consideration here is called "P-factor," which is the tendency of a propeller to produce more thrust from one side of its disc than from the other. P-factor usually affects the aircraft in the same manner as torque, and it is exacerbated by slow speeds and hard turning. Since even more rudder is usually required in the direction of a turn to maintain balanced flight, there may be conditions under which sufficient rudder power is just not available. The resulting unbalanced flight (slip) may cause loss of aircraft control. Generally the high wing (i.e., the outside wing in a turn) will stall, causing the aircraft to "depart" controlled flight with a rapid roll toward the stalled wing. This phenomenon has been used to good effect in combat, since it is more pronounced in some fighters than in others, and because prop-rotation direction may be reversed between combatants. The following World War II combat example to this tactic involves the P-38J Lightning versus the German Fw 190. The P-38 is a twin-engine fighter with counter-rotating props and essentially no net torque or P-factor. My flight of four P-38's was bounced by twenty-five to thirty FW-190's of the yellow-nose variety from Abbeville. A string of six or more of them got in behind me before I noticed them, and just as No. 1 began to fire, I rolled into a right climbing turn and went to war emergency of 60 inches manifold pressure. As we went round and round in our corkscrew climb, I could see over my right shoulder the various FW-190 pilots booting right rudder attempting to control their torque at 150 mph and full throttle, but one by one they flipped over to the left and spun out. ---------- Paul O'Neill pvo@oce.orst.edu Coastal Imaging Lab OSU--Oceanography Corvallis, OR 97331 503-754-3251
willner@cfa.harvard.edu (Steve Willner) (11/08/89)
From: willner@cfa.harvard.edu (Steve Willner) >From article <11069@cbnews.ATT.COM>, by pvo3366@sapphire.oce.orst.edu (Paul O'Neill), who was either quoting or following up a quote from _Fighter Combat Tactics and Maneuvering_ by Robert L. Shaw: > Torque may also have an effect on turn performance, particularly with > high-powered prop fighters at slow speed. The effects of engine torque > must generally be offset by rudder power to maintain balanced flight. The main point of the article seems right, but the terminology is a bit confused. "Torque" is a roll force, counteracted with aileron. The propellor spins one way, and air resistance imparts a force to the aircraft in the opposite direction. The magnitude of the torque force depends mostly on power, and at low airspeed control authority may be insufficient to counter the torque. > Normally under these conditions considerable right rudder will be required > to balance the torque of a prop turning clockwise (when viewed from behind), > and vice versa. Another consideration here is called "P-factor," which is the > tendency of a propeller to produce more thrust from one side of its disc than > from the other. The explanation of p-factor is simple enough: as _aircraft_ angle of attack increases, the _propellor_ angle of attack becomes greater on the descending than on the ascending side of the arc. This produces more thrust on the descending side, which produces a _yaw_ force to the opposite side. For conventional rotation, the descending side is the right, the yaw force is to the left, and right rudder is needed to counter the yaw. Another yaw force comes from the fact that the upwash from the prop is moving crosswise when it encounters the vertical stabilizer. (For conventional rotation, this is left-to-right.) This produces a yaw force in the same direction as p-factor. The force is generated because the vertical stabilizer extends above but not (much) below the engine centerline. This force is mostly related to engine power, while p-factor depends on both engine power and angle of attack. > there may be conditions under which sufficient rudder power is just not > available. The resulting unbalanced flight (slip) may cause loss of aircraft > control. Generally the high wing (i.e., the outside wing in a turn) will > stall, causing the aircraft to "depart" controlled flight with a rapid roll > toward the stalled wing. I must be missing something here. Flying with insufficient rudder relative to bank angle is indeed a slip, but I don't see why it should lead to loss of control. More dangerous is the _skid_, which is _too much_ rudder relative to bank. If a stall occurs while skidding, entry into a spin can be very rapid. Furthermore, why should the _outside_ wing stall first? I would think the _inside_ wing would be flying at higher angle of attack. The case should be analogous to trying to turn without using rudder at all, which normally just produces lots of adverse yaw and little turning. The penalty of a slip is generally just loss of performance because of greatly increased drag. > This phenomenon has been used to good effect in combat, [FW 190's in climbing right turn stall and roll left] I don't question the narrative, but I do wonder about the explanation. Perhaps what happened could have been that _both_ wings stalled (an "accelerated stall" probably), and then the torque _rolled_ the planes to the left. If this is the correct explanation, increased rudder authority would not have prevented the stall, though it would have allowed the 190's a higher climb rate, so the pilots might not have been tempted to reach a stall. There still would have been drag associated with the rudder, though, and the general point that the 190's would climb slower in a right turn than in a left turn is certainly valid. (Assuming they had the normal direction of propellor rotation, of course.) ------------------------------------------------------------------------- Steve Willner Phone 617-495-7123 Bitnet: willner@cfa 60 Garden St. FTS: 830-7123 UUCP: willner@cfa Cambridge, MA 02138 USA Internet: willner@cfa.harvard.edu