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#1 =FB=VikS

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Posted 18 June 2010 - 18:14

Here you can discuss Current ROF Airplanes Flight Model on noted HERE issues.
Source topic is HERE.
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#2 gavagai

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Posted 19 June 2010 - 12:28

The first one that's missing from the standard list is the Sopwith Camel. :D

Image
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#3 IRFC_SmokinHole

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Posted 19 June 2010 - 23:54

I have nothing contructive to contribute to this topic but I do want to be on the first page of what will be 45 pages of:

guesses,
assuptions,
WAGs,
conjectures,
interprolations,
extrapolations,
half-truths,
misunderstandings,
fabrications,
revisionisms,
insults and,
hurt feelings.

(oh, and misspellings. )

Enjoy the show!
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#4 hq_Reflected

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Posted 20 June 2010 - 09:00

What about the curiously high TAS of some rotaries like th DR1 or the D.VIII?

Attached File  TAS_ROF.jpg   95.85KB   5104 downloads
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#5 Eldur

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Posted 20 June 2010 - 10:13

Seems that nobody cares about the D.H.2 top speed. It's 93mph (150km/h) in every source I've seen so far. Maybe I've missed the single one that tells it's just 20km/h slower :lol:
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#6 hq_Jorri

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Posted 20 June 2010 - 10:49

Eldur, you can post those sources here and they will be taken seriously and not be lost in a flood of speculation.

Are people throwing the towel in the ring just now neoqb is showing their interest and organising the discussion? :roll:
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#7 Huetz

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Posted 20 June 2010 - 11:25

Well I am definately not. (Why would you throw towels around anyways? :lol: )
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#8 hq_Reflected

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Posted 20 June 2010 - 11:50

Seems that nobody cares about the D.H.2 top speed. It's 93mph (150km/h) in every source I've seen so far. Maybe I've missed the single one that tells it's just 20km/h slower :lol:

84 mph is the best i could get out of her at treetop level :?
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#9 MiG-77

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Posted 20 June 2010 - 11:58

Seems that nobody cares about the D.H.2 top speed. It's 93mph (150km/h) in every source I've seen so far. Maybe I've missed the single one that tells it's just 20km/h slower :lol:

84 mph is the best i could get out of her at treetop level :?

That 92mph speed is for DH-2 with 20.8 gallon tank. In game DH-2 has larger 26 gallon tank and it was slower in speed (and climb). At 10 000ft it was 7mph slower (no test speed for ground level).

Made quick test on DH-2 at 1800m (~6000ft) and I could get 119km/h indicated airspeed = ~133km/h true airspeed (by adding just simple 2% for every 1000ft altitude). Windsock list 129km/h at 6000ft to DH-2 with 26 gallon tank. Seems correct to me.
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#10 hq_Reflected

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Posted 20 June 2010 - 12:27

Topic: SE5a Stall speed:

RoF data (confirmed by tests: 56 mph (90 kph) - 100% fuel, no ammo

real deal: 50 mph landing speed, 45 mph (max) touchdown speed.

Attached File  SE5a flight characteristics F904 flight report 1977 @ Shuttleworth.rar   443.59KB   179 downloads

(Thanks, Catfish ;) )

also:

The tail is raised and
within a few seconds a flying speed of around 50 to 55 mph is reached. The aircraft flies off
the ground with a will and settles into a natural climb at about 60 to 65 mph.
Both control power and harmonisation are good. The SE is very similar to the Tiger moth but
with higher roll rate and slightly heavier controls. There is also the absence of the inertia
caused by the Tiger‟s heavy centre section fuel tank. The climb is rapid and as briefed, slight
oil mist/smoke is seen to emit from the radiator area and the starboard side of the engine
cowl. After take off, the rpm are reduced to 1900 to reduce engine wear, and coolant
temperature and radiator flaps are monitored and regulated respectively.
An appropriate height for stalling is soon reached and the slow end of the flight envelope can
be essayed. First, engine management must be carried out and the radiator shutters are closed
as the throttle is retarded. The latter must be done slowly as fast engine modulation brings
unwanted stress on the engine and may lead to a damaging backfire. The stall break occurs at
about 45 mph
with more than adequate buffet as a warning and a wings level nose drop as an
indicator.

Roger ИDodge’ Bailey The Shuttleworth Collection Old Warden Aerodrome Biggleswade, Beds, UK (Original SE5a)

Next, slow flight and stalls are explored, a good
idea to check before landing…. again nothing unusual other than the fact that this airplane is rather
easy to fly. Adjusting the elevator trim allows the SE5a to be flown hands off something I’m not used
to in a WW1 fighter. A few more stalls are investigated and a power off stall speed of 43 mph is
noted.

(Vintage aviator - replica)
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#11 gavagai

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Posted 20 June 2010 - 16:53

Has anyone tested the DH2's best TAS instead of just looking at its best IAS?
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#12 Mogster

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Posted 20 June 2010 - 16:57

Maybe we should add the Albatros roll rate to this.

I agree there's evidence for a speed increase but it seems to roll way better than contemporary and current reports from replicas suggest. There's a thread over at the aerodrome with quotes from WW1 pilots, pilots like Roderic Dallas, Cecil lewis and McCudden comment on the poor roll reponse of the examples they flew. Gene Demarco who flew the Vintage Aviator replica wrote in Classic Wings last year that their replica Albatros Va has poor roll and heavy aileron response along with twitch elevator.

http://www.theaerodr...html#post508754" onclick="window.open(this.href);return false;">http://www.theaerodr...com/forum/aircr … post508754

You can't find any of this in the ROF Albatros fm.
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#13 hq_Reflected

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Posted 20 June 2010 - 17:27

Has anyone tested the DH2's best TAS instead of just looking at its best IAS?

84 MPH at treetop level. Convert it to TAS if you wish :)
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#14 gavagai

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Posted 20 June 2010 - 17:32

Has anyone tested the DH2's best TAS instead of just looking at its best IAS?

84 MPH at treetop level. Convert it to TAS if you wish :)

The best TAS might not be at sea level.
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#15 MiG-77

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Posted 20 June 2010 - 17:59

Has anyone tested the DH2's best TAS instead of just looking at its best IAS?

84 MPH at treetop level. Convert it to TAS if you wish :)

The best TAS might not be at sea level.

It should be on DH-2. But again, game has late DH-2 variant with bigger fuel tank. It was slower than earlier one (93mph was max speed of earlier DH-2).
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#16 hq_Reflected

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Posted 20 June 2010 - 18:05

Has anyone tested the DH2's best TAS instead of just looking at its best IAS?

84 MPH at treetop level. Convert it to TAS if you wish :)

The best TAS might not be at sea level.

Yes, but the sources refer to TAS at sea level. As for the bigger fuel tank. Would they have replaced the DH2 by a slower variant? :?
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#17 MiG-77

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Posted 20 June 2010 - 18:13

Yes, but the sources refer to TAS at sea level. As for the bigger fuel tank. Would they have replaced the DH2 by a slower variant? :?

They wanted more endurance. Bigger fuel tank -> more weight -> slower speed (and climb). Anyway it is clearly mentioned in DH-2 datafile that later planes were infact slower (but had longer endurance).
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#18 Vati

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Posted 23 June 2010 - 08:51

Maybe we should add the Albatros roll rate to this.

I agree there's evidence for a speed increase but it seems to roll way better than contemporary and current reports from replicas suggest. There's a thread over at the aerodrome with quotes from WW1 pilots, pilots like Roderic Dallas, Cecil lewis and McCudden comment on the poor roll reponse of the examples they flew. Gene Demarco who flew the Vintage Aviator replica wrote in Classic Wings last year that their replica Albatros Va has poor roll and heavy aileron response along with twitch elevator.

http://www.theaerodr...html#post508754" onclick="window.open(this.href);return false;">http://www.theaerodr...com/forum/aircr … post508754

You can't find any of this in the ROF Albatros fm.
RFC/RAF pilots were mentioning that control forces were higher for lateral controls than on their planes and not that roll was worse (it is thus they are amazed how could Germans fly them so well). They also flew D.V not D.Va, which has totally different rigging and was indeed a problem, which resulted in using again the wings from D.III in D.Va.
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#19 Eldur

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Posted 24 June 2010 - 18:10

That 92mph speed is for DH-2 with 20.8 gallon tank. In game DH-2 has larger 26 gallon tank and it was slower in speed (and climb). At 10 000ft it was 7mph slower (no test speed for ground level).

Makes sense. "Usual" data is about the one without the tank on top of the top wing. I'd like to have an early D.H.2 anyway :D
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#20 Mogster

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Posted 25 June 2010 - 10:34

Maybe we should add the Albatros roll rate to this.

I agree there's evidence for a speed increase but it seems to roll way better than contemporary and current reports from replicas suggest. There's a thread over at the aerodrome with quotes from WW1 pilots, pilots like Roderic Dallas, Cecil lewis and McCudden comment on the poor roll reponse of the examples they flew. Gene Demarco who flew the Vintage Aviator replica wrote in Classic Wings last year that their replica Albatros Va has poor roll and heavy aileron response along with twitch elevator.

http://www.theaerodr...html#post508754" onclick="window.open(this.href);return false;">http://www.theaerodr...com/forum/aircr … post508754

You can't find any of this in the ROF Albatros fm.
RFC/RAF pilots were mentioning that control forces were higher for lateral controls than on their planes and not that roll was worse (it is thus they are amazed how could Germans fly them so well). They also flew D.V not D.Va, which has totally different rigging and was indeed a problem, which resulted in using again the wings from D.III in D.Va.

Gene Demarco describes the aileron reponse on the Vintage Aviator D5a as being disappointing, i don't see how anyone could be disappointed with the ROF Albi's

Found this table of theoretical turn circles in Leon Bennett's "Gunning for the Red Baron"

Entente aircraft data from NASM archive, German from Flugsport 1919.

Image
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#21 NakedSquirrel

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Posted 28 June 2010 - 09:40

I do not believe the Albatros D.II is modeled correctly. It turns on par if not better than the Albatros D.III. The Albatros D.III has both a better rate of climb as well as a more powerful engine (20hp). I do not see any feasible way that the D.II would be able to maintain this level of maneuverability because it does not have the lift or speed of the D.III.

Here is a series of pictures taken from the same altitude (.k3) comparing the turn rate of both planes. Both planes are on the deck with their right wings cutting grass as I try to turn as efficiently as the planes will let me without hitting the ground.

RED: Albatros D.III
Blue: Albatros D.II
Image

As you can see the planes turn at a very similar rate. Both planes complete a full circle turn at nearly the same time. 12 seconds.

I tried to repeat this experiment by slightly reducing the throttle in the Albatros D.III to match the RPM output of the 160hp engine in the Albatros D.II, but the turn radius doubled. It wound up being about as big as all 4 photos combined.
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#22 WW1EAF_Ming

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Posted 28 June 2010 - 11:52

I try to turn… efficiently

You'd first need to find out if your turning is typically efficient BB, in order to say that your findings are typical

That would be the first test, to find out if you are a typical pilot

You'd work out an average turning radius and compare that to reported/probable historical turn radii

This way you avoid giving too much weight to your own test results if you're looking for a more general result.

Logic being: you may be an outlying Ace or an outlying rookie

Ming
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#23 J2_squid

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Posted 28 June 2010 - 12:26

An Fe2b can out turn a DR1?
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#24 MiG-77

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Posted 28 June 2010 - 12:35

I think it is just typical "lets compare wingloading" to get those results. In those, bombers wihtout bombs, get pretty amazing results (IE Gotha has better wingloading than most scouts) ;)
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#25 J2_squid

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Posted 28 June 2010 - 12:37

Okay, put it another way.

An DH2 can out turn a DR1?
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#26 MiG-77

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Posted 28 June 2010 - 12:41

Okay, put it another way.

An DH2 can out turn a DR1?

By just looking wingloading, yes. But to take all other important factors, hard to tell. IE that comparison is totally misleading as it wont take account gap/chord ratio, stagger and wing profile. It just compares wingloading…
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#27 J2_squid

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Posted 28 June 2010 - 12:45

Thanks Mig, makes sense. I cited that table in another discussion :oops:
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#28 NakedSquirrel

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Posted 28 June 2010 - 17:59

I try to turn… efficiently

You'd first need to find out if your turning is typically efficient BB, in order to say that your findings are typical

That would be the first test, to find out if you are a typical pilot

You'd work out an average turning radius and compare that to reported/probable historical turn radii

This way you avoid giving too much weight to your own test results if you're looking for a more general result.

Logic being: you may be an outlying Ace or an outlying rookie

Ming

Turning radius is about 190 feet in both of the above cases. Both of these aircraft have the potential to pull a tighter turn, but they would loose altitude. Since the planes are both on the deck, obviously there was no room for this.

I did a good dizzying number of turns both to the right and to the left in both planes. I could have taken pictures of half a dozen turns, but I don't want to flood the topic. I simply took screenshots of two 'random' circles. The planes seemed to match up in both time and circumference.

During the test I did find the D.III a little more difficult to handle than the D.II. The D.III liked to side slip towards the ground. It took me some time to get in the groove of making a good, tight turn.

It is hard to get any good data on the Albatros D.II vs the D.III. I wish we had better documentation. I think it is an interesting change of design to cut down on the size of the lower wing. With these designs so similar, I wonder how much of a difference the change had. I am not trying to argue that the sesquiplane design was more/less efficient in a turn than the biplane design, but there should be a more distinct difference in handling between these two aircraft.

The D.III has the late war 180 hp Mercedes engine. It is lighter , and it has a better rate of climb. There is no need to split hairs here, the difference should be obvious.


Power (h.p.): 160hp
sea level — 164kph
Empty weight (kg): 673
Takeoff weight (kg): 898
1000 m — 4 min. 27 sec


Power (h.p.): 180hp
sea level — 170
Empty weight (kg): 660
Takeoff weight (kg): 885
1000 m — 3 min. 57 sec.
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#29 WW1EAF_Ming

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Posted 28 June 2010 - 23:54

People like a challenge I think you'll find in the Tightest Turner Memorial Prize. Awarded posthumously :)

Ming
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#30 HotDog

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Posted 29 June 2010 - 06:52

I think some understanding of turn radius and maneuverability is important here. I'm not refuting anybodies findings in this thread so far or even questioning their conclusions but I do believe there is some confusion as to what's important in a dogfight for success.

Maneuverability with regards to a fighter is widely considered to be the SUSTAINED RATE of change of its thrust vector. This excludes instantaneous turn rate which can be substantially higher but induces enough drag to make it a very temporary performance. An SE5 can achieve remarkable instant rate even from level flight due to its energy, it cannot maintain sustained rate like many other fighters though.

Maneuverability is NOT roll rate. Roll rate is another attribute with some different contributing characteristics. Roll rate is the rate of change of a fighters LIFT vector. Planes like the P-47 Thunderbolt were capable of incredible roll rate but were not considered Maneuverable. Some pilots have termed this as 'agility' but that term is far from being common usage. Some of the fastest rolling planes are energy fighters for same reasons that make them fast.

TURN RADIUS is seperate to Maneuverability as it is the physical distance a fighter turns in the sky and although it has a relationship with TURN RATE a plane can have a small turn radius and be completely outclassed in TURN RATE. A plane can therefore have a small turn radius and still be considered relatively unmaneuverable, like an EIII.

Finally, how does this work in dogfighting success? Without going into detail, in a nose-to-tail (rate fight) the more maneuverable plane out-turns the other and can achieve a 6'oclock shot. It doesn't even need to have a small radius because it can displace its flight circle and cut inside the other's arc with a much larger radius. (think two intersecting circles rather than one)

In a nose-to-nose (radius fight) confrontation, the fighter with the small radius can turn inside the flight path of the other fighter even if it has a higher rate (the opponent will overshoot). A series of these nose-to-nose turns would be considered your typical 'scissors' maneuver.

I only thought it important to get this straight as I see a lot of posts here confusing different aspects of planes abilities and calling them 'maneuverability'. The graph several posts above shows the DH2 has a small radius and while that may be true (because it is slow) it says nothing about its turn rate or maneuverability of any of those fighters.
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#31 WW1EAF_Ming

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Posted 29 June 2010 - 09:16

During the test I did find the D.III a little more difficult to handle than the D.II. The D.III liked to side slip towards the ground. It took me some time to get in the groove of making a good, tight turn.

Good stuff BB.

Yes there's also the vertical component to consider, with some planes having tight turns to begin with but then descending in that forced-slipping, while other planes will be able to maintain the flat turn. Flattish anyway. Flatter. I know what I mean :) (like in Il-2 while we flat-turn in a Hurricane while the E4 perches above)

In that nice WW1-Russia movie that's around there's a plane (later on) with a 400HP engine. That'll be a turner I bet. Or anything it wants :)

But the power of the engine must be very important is what I mean for maintaining the flat-turn without descending, slipping down when attempting to maintain the same height, letting a plane with a less powerful engine drop down in the turnings

Ming
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#32 Chill31

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Posted 29 June 2010 - 22:47

Topic: SE5a Stall speed:

RoF data (confirmed by tests: 56 mph (90 kph) - 100% fuel, no ammo

real deal: 50 mph landing speed, 45 mph (max) touchdown speed.



(Thanks, Catfish ;) )

also:

The tail is raised and
within a few seconds a flying speed of around 50 to 55 mph is reached. The aircraft flies off
the ground with a will and settles into a natural climb at about 60 to 65 mph.
Both control power and harmonisation are good. The SE is very similar to the Tiger moth but
with higher roll rate and slightly heavier controls. There is also the absence of the inertia
caused by the Tiger‟s heavy centre section fuel tank. The climb is rapid and as briefed, slight
oil mist/smoke is seen to emit from the radiator area and the starboard side of the engine
cowl. After take off, the rpm are reduced to 1900 to reduce engine wear, and coolant
temperature and radiator flaps are monitored and regulated respectively.
An appropriate height for stalling is soon reached and the slow end of the flight envelope can
be essayed. First, engine management must be carried out and the radiator shutters are closed
as the throttle is retarded. The latter must be done slowly as fast engine modulation brings
unwanted stress on the engine and may lead to a damaging backfire. The stall break occurs at
about 45 mph
with more than adequate buffet as a warning and a wings level nose drop as an
indicator.

Roger ИDodge’ Bailey The Shuttleworth Collection Old Warden Aerodrome Biggleswade, Beds, UK (Original SE5a)

Next, slow flight and stalls are explored, a good
idea to check before landing…. again nothing unusual other than the fact that this airplane is rather
easy to fly. Adjusting the elevator trim allows the SE5a to be flown hands off something I’m not used
to in a WW1 fighter. A few more stalls are investigated and a power off stall speed of 43 mph is
noted.

(Vintage aviator - replica)

Frank Tallman "flying the old planes"
Flying an original SE5 with a Hisso engine


"Settling back to cruise, I locked my belt and brought the stick back for a stall. It pays off gently, but with a sharp right-wing drop at an indicated 52 mph. Invariably, in a stall, the right wing dropped."

*Personally, I find it very odd for him to have a power off stall at 43 mph. given that he took off at 50-55…Your stall speed in ground effect is LOWER than your stall speed flying up in the open air AND it should be significantly lower than your POWER OFF stall speed…I can explain the physics/aerodynamics if you really want…
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#33 hq_Reflected

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Posted 30 June 2010 - 06:10

Chilli, I don't know what explanation do you have for this, but I'm all ears. The Shuttleworth SE is a real one, real engine, real guns (no ammo) real fuel tanks, same weight. It touches down at 45 mph, and we, in RoF stall at 56. That's 125% ! A huge difference…

Oh, and by the way, the SW SE has a 200 HP Viper, while the SE flown by Tallman had a 180 HP Hisso.
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#34 Kwiatek

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Posted 30 June 2010 - 20:32

" 3) Pfalz D.IIIa - maneuvers too good, horizontal speed too low "

Good to hear about planned fix for Pfalz DIIIa unrealistic manouvers in ROF but i wonder what with some other German planes like Albatros and Fokker DVII?

I post about these in other topic but i think Neoqb should check these things also.


I made 3 short videos with Se5A, Albatros DVa and DVII when i test how they react in sharp turn and pull up with maximum deflection of stick.


First video is how plane with good FM should stall in hard turn. Se5a stall immidietly in such turn when reach critical angle of attack.

http://www.youtube.c...h?v=88PoK6Q05ck" onclick="window.open(this.href);return false;">



Second and Third video is with German planes Albatros Dva and Fokker DVII. They dont have accelerate stall at all and could do some unrealistic manouvers. Look how they make loop - Fokker DVII could make a loop at maxium deflection of stick at high speed near in a spot ( burn all energy in such manouvers but has not accelerated stall and make manouvers near in a spot)


Albatros:

http://www.youtube.c...h?v=tMW4-oRF9uE" onclick="window.open(this.href);return false;">

DVII

http://www.youtube.c...h?v=Xg1ZW7jl4-U" onclick="window.open(this.href);return false;">



Here are pilots notes about these planes :


Se5A

"To get a better feel for what this airplane can do, steep turns, lazy eights and wingovers are attempted, all easily carried out but an excessive amount of adverse yaw is experienced.
The adverse yaw is easily compensated for, by balancing aileron application with rudder and doesn’t prove to be a problem at all. Next, slow flight and stalls are explored, a good idea to check before landing…. again nothing unusual other than the fact that this airplane is rather easy to fly. Adjusting the elevator trim allows the SE5a to be flown hands off something I’m not used to in a WW1 fighter. A few more stalls are investigated and a power off stall speed of 43 mph is noted.

With the power pushed up a bit, a conservative top speed of 115- 120 mph is achieved!
I would expect during wartime even this top speed would be increased to the reported numbers of about 138 MPH. The only aircraft that could come close was the Fokker DVII, so the SE5a was faster than anything out there and very competitive with the later produced DVII. The performance doesn’t seem to diminish with altitude either, it can maintain 120 mph right up to about 15,000 ft. After the formalities of recording figures for temperatures, pressures and airspeeds, it’s time to really get a feel for the new plane. I am still amazed that it is so easy to fly and feels so stable. Turns in either direction are simple as long as they are coordinated with the rudder."


"At the time the SE5a entered service, pilots were arriving at the Front with fewer than 20 hours of flying time, so a plane that could be flown by pilots of limited flying experience was very well accepted. There were far fewer accidents than those experienced with many of the Sopwith or Nieuport designs. While the highly maneuverable designs were better suited to skilled pilots with many hours of flight time, the SE.5a design was entirely different. Easy to fly, stable and forgiving, even a mediocre pilot could capitalize on the steadiness of the aircraft, firing at the enemy from further away with a greater degree of accuracy."


Besides:

Se5A had lower take off weight and bigger wing area then German Scouts or DVII so it had lower wingloading. It had less camber airfoil then Albatros or Pfalz DIIIa so i expect it has little lower CLmax but other hand it had more gentle stall above critical angle of attack then German Scouts. These really prety good is confirmed by German pilots opinion about German Scouts:

Albatros DIII:

" Apart from its structural deficiencies, the D.III was considered pleasant and easy to fly, if somewhat heavy on the controls. The sesquiplane arrangement offered improved climb, maneuverability, and downward visibility compared to the preceding D.II. Like most contemporary aircraft, the D.III was prone to spinning, but recovery was straightforward."


Pfalz DIII:

"German pilots variously criticized the Pfalz’s heavy controls, low speed, lack of power, or low rate of climb compared to the Albatros. The D.III slipped in turns, leading to crashes when unwary pilots turned at very low altitudes. Moreover, the Pfalz stalled sharply and spun readily. Recovery from the resulting flat spin was difficult, though some pilots took advantage of this trait to descend quickly or evade enemy aircraft"



Se5A:

" To get a better feel for what this airplane can do, steep turns, lazy eights and wingovers are attempted, all easily carried out but an excessive amount of adverse yaw is experienced.
The adverse yaw is easily compensated for, by balancing aileron application with rudder and doesn’t prove to be a problem at all. Next, slow flight and stalls are explored, a good idea to check before landing…. again nothing unusual other than the fact that this airplane is rather easy to fly.

"Easy to fly, stable and forgiving, even a mediocre pilot could capitalize on the steadiness of the aircraft"


And i think Neoqb did pretty good job with FM of SE5a ( besides these stupid elevator issue and absence of elevator trimm) - these planes fly very natural, have accelerated stall but is quite easy to fly and stall warning is very good.

I cant say the same about German Scouts and Fokkers by Neoqb. They dont behave like combat planes but rather like RC models.

I hope Neoqb will check these things carefully and make all German planes to fly more like RL combat planes not flying kites.

I think the same like Pflaz DIIIa it should be checked and fixed in the same way.
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#35 Chill31

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  • Posts: 1891

Posted 01 July 2010 - 14:09

Kwiatek, you need to have sources for your pilot notes…the name of the author and book is a good start. Otherwise, we can simply put in quotes whatever we want…
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#36 Chill31

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Posted 01 July 2010 - 14:26

Reflected,

My goal in posting conflicting data to yours is NOT to prevent changes from being made. Each plane of the same type will have a different "personality" and will fly slightly different from the one sitting right next to it on the flight line. So I like to take all the data (which is probably very good) and average it so that you are right in the middle.

Anyway, to explain why a 43 mph power off stall paired with a 50-55 mph take off speed contradicts itself a little bit. Also, when accompanied by Frank Tallman's info, I think 43 mph power off may be a little off.

When you perform a power off stall at altitude, the only vertical force acting on the plane to keep it in the air is lift produced by the wing. The plane begins to fall (stall) when the weight component toward the earth is greater than the lift produced by the wing. With power off, this could be 60 mph lets say. Now if I do a power on stall, there are 2 vertical forces keeping the plane in the air: lift from the wing, and thrust from the engine. This means that the engine/propellor can carry some of the weight that the wing would have to carry and the plane will now stall at a lower airspeed than 60.

On to ground effect…ground effect is where the earth reduces induced drag and essentially makes the wing more efficient. This is why you can actually take off in most airplanes well below safe flying airspeed and upon exiting ground effect (about half your wingspan) you can suddenly be falling back to earth. So a landing speed of 43 mph using a 3 point landing (tail low stall) means that his out of ground effect stall should be higher than 43mph.

Also keep in mind, that higher AoA (angle of attack), such as near stall, introduces more error into the airspeed indication. If there are any variations between aircraft pitot systems, this could account for some variation in numbers (another reason to average data)

Hope this helps…
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#37 hq_Reflected

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Posted 01 July 2010 - 18:01

OK Chili, thanks for expaining, I understand what you wrote - and learned a lot from it. However, I asked a real pilot and he said that the touchdown speed is always superior to the stall speed. Also, no one tries to take off until a safe speed is achived, hence the 50-55 mph takeoff speed (which is still lower than our 56 mph stall speed) The touchdown speed is "maximum 45 mph" according to the document. Of course, planes should have a personality, but 43 mph vs 56 is a huge difference, that's what made me think in the first place. I tried to look into many things:
-Is the SW SE5a lighter than a wartime one? - no, apart fro mthe ammo load
-Is it an original one, with the original parts (same engine, etc..) - yes

So even if data derived from tests made with it can not be carved in stone, still they should be a very good reference, and again, it's 43 vs 56.

Also, Tallman's SE is not a 100% original one, it has a different (weaker) engine, so we should consider those data less likely to be accurate than the SW report (which is a wartime SE minus ammo)

So even after considering your points I think the SE5a's stall speed should definitely be well below 50mph at worst. :roll:
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#38 NakedSquirrel

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Posted 02 July 2010 - 20:36

Image

Okay, put it another way.

An DH2 can out turn a DR1?

I think think we are missing a key point here. Something about this chart was bugging me and it finally dawned on me why. So let me put this a different way to punctuate why: A Sopwith Dolphin could easily out turn a Bf109, why did the British ever bother with the Spitfire?

OK, so it's a bit of an exaggeration since the Bf109 can go about 400 kph faster, but I think it makes the point that turning radius won't mean the same as turn speed. I think a DH2 could make a tighter circle than an Dr1, but a Dr1 would probably make its full circle in half the time. I don't think the DH2 would stand much of a chance in a dogfight against the Albatros fighters because of its low speed and terrible climb rate.
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#39 sturmkraehe

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Posted 02 July 2010 - 20:50

Turn radius Chart is based on wing loading calculation as clearly stated by the note. Therefore not a reliable definite source … so carefull with this one. It is NOT an original source.
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#40 ImPeRaToR

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Posted 02 July 2010 - 21:57

wing loading is also relative and the effective lift of the wing area depends on the gap and wing chord (afaik).
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