Why is the Spitfire Mk IX still unstable??

[bongodriver]

Ah cool, so you get to ride in it in full combat load out... nice... :music_whistling:

 

When building an FM, I think all you can go on is raw data, the anecdotes help round it out of course... ED is good at letting knowledgeable pilots try their stuff out and give input, ie the P-51D.

 

Most if not all Spitfires have wing tanks in place of guns so not far off, not flow the Spit yet myself.

 

oh...:music_whistling:

[NineLine]

Most if not all Spitfires have wing tanks in place of guns so not far off, not flow the Spit yet myself.

 

If you get to, I hope you wont be taking a historic aircraft such as that and flying it like a pilot from the 1940's, flying on the edge, in a manner of flying to save their life...

 

Point being, nobody flies a Spitfire like it was flown in combat back in the day... so Modern pilots have good info, but not all of it.

[bongodriver]

If you get to, I hope you wont be taking a historic aircraft such as that and flying it like a pilot from the 1940's, flying on the edge, in a manner of flying to save their life...

 

Point being, nobody flies a Spitfire like it was flown in combat back in the day... so Modern pilots have good info, but not all of it.

 

Well if I ever do I wont be concerned about it, everyone I know who flies them certainly have no reservations about it's capabilities, you'd be surprised just how close to the edge modern day Spits have been flown by some of the private operators, the BBMF are certainly more cautious.

[NineLine]

Well if I ever do I wont be concerned about it, everyone I know who flies them certainly have no reservations about it's capabilities, you'd be surprised just how close to the edge modern day Spits have been flown by some of the private operators, the BBMF are certainly more cautious.

 

I have no doubt people push them hard in some cases, but I highly doubt they spend much time on the edge, or as with combat, over the edge... anyways we are getting off the beaten track (topic), I think we can agree, that more experience might convey something is easier to do than someone with less experience... so that needs to be taken into account.

[bongodriver]

I have no doubt people push them hard in some cases, but I highly doubt they spnd much time on the edge, or as with combat, over the edge... anyways we are getting off the beaten track, I think we can agree, that more experience might convey something is easier to do than someone with less experience... so that needs to be taken into account.

 

Indeed we do agree, it's just what Crumpp is trying to achieve is to make the Spitfire difficult for everyone no matter what level of experience.

 

Anyway, we are not off the beaten track, we are still discussing Spitfire stability and handling characteristics.

Edited October 21, 2015 by bongodriver

[NineLine]

Indeed we do agree, it's just what Crumpp is trying to achieve is to make the Spitfire difficult for everyone no matter what level of experience.

 

Honestly I am not sure he is trying to do that, I think he is trying to show what level of instability he believes it has by the available reports he has, I am not saying he is right or wrong, honestly, no offence to anyone, but thats Yo-Yo's job, I'll let him take care of that, and I will see what we start flying her around...

 

All that said, it does seem like the Spit didnt handle like it was on rails, so I am leaning towards there being some instabilities, but really I am not up on it enough to say either way, this is just a discussion, not a winner takes all and makes the FM contest, so try not to get too emotionally attached to it and take it for what it is... agree, dont agree... but dont get worked up about it. Yo-Yo will gather what he needs to make a great FM has he has in the past.

[MiloMorai]

FIGURE 4.5. Supermarine Spitfire airplane. A high-performance fighter noted for its role in the Battle of Britain and throughout WW II, the Spitfire had desirably light elevator control forces in maneuvers and near neutral longitudinal stability. Its greatest deficiency from the combat standpoint was heavy aileron forces and sluggish roll response at high speeds.

http://history.nasa.gov/monograph12/ch4.htm

[NineLine]

FIGURE 4.5. Supermarine Spitfire airplane. A high-performance fighter noted for its role in the Battle of Britain and throughout WW II, the Spitfire had desirably light elevator control forces in maneuvers and near neutral longitudinal stability. Its greatest deficiency from the combat standpoint was heavy aileron forces and sluggish roll response at high speeds.

http://history.nasa.gov/monograph12/ch4.htm

 

Yeah, this is the report here I think http://jsbsim.sourceforge.net/spit_flying.pdf

[Cripple]

Honestly I am not sure he is trying to do that, I think he is trying to show what level of instability he believes it has by the available reports he has, I am not saying he is right or wrong, honestly, no offence to anyone, but thats Yo-Yo's job, I'll let him take care of that, and I will see what we start flying her around...

 

All that said, it does seem like the Spit didnt handle like it was on rails, so I am leaning towards there being some instabilities, but really I am not up on it enough to say either way, this is just a discussion, not a winner takes all and makes the FM contest, so try not to get too emotionally attached to it and take it for what it is... agree, dont agree... but dont get worked up about it. Yo-Yo will gather what he needs to make a great FM has he has in the past.

 

Well said.

 

I suspect that all parties here are actually more in agreement that some of the posting would indicate. I don't think the OP is suggesting that the Spit IX bucked like Bronco, but that there was some inherent lack of stability (whether he can "prove" this is a separate issue, but it seems she didn't fly like she was on rails - as you say). Similarly, I too have read the favourable contemporary reports about the Spitfire's handling (compared to other contemporary aircraft, one presumes), and concur that these are at odds with the OP's assertion, but am cautious about use of anecdotal reports as evidence - particularly when the underlying concept of stability has not been defined to the satisfaction of all parties prior to discussion commencing.

 

In short, I too am on the fence.... but it is an interesting point to discuss and ponder.

 

Personally I hope the option of flying with a full rear tank is in the final release. It would be interesting for us to see how "stable" or otherwise she really is. Which is the beauty of simulators - you push the envelop and experiment in the way you just don't with a (very expensive!) flying museum piece.

[bongodriver]

Honestly I am not sure he is trying to do that, I think he is trying to show what level of instability he believes it has by the available reports he has, I am not saying he is right or wrong, honestly, no offence to anyone, but thats Yo-Yo's job, I'll let him take care of that, and I will see what we start flying her around...

 

All that said, it does seem like the Spit didnt handle like it was on rails, so I am leaning towards there being some instabilities, but really I am not up on it enough to say either way, this is just a discussion, not a winner takes all and makes the FM contest, so try not to get too emotionally attached to it and take it for what it is... agree, dont agree... but dont get worked up about it. Yo-Yo will gather what he needs to make a great FM has he has in the past.

 

You only have to see the level of obsession with this particular topic this poster shows across the internet, we don't even have a Spit in game yet so why start this topic?

 

No aircraft flew on rails, there were instabilities in the Spit with a rearward CG just like any aircraft, it's the Spitfires light controls that made handling those instabilities require a touch of finesse, the same lightness made handling those characteristics so easy, you can hear Al Pinner say as much in the video, you could pitch too much with ease, you could correct it with similar ease, as mentioned the lightness was 'desireable' in a fighter and is primarily the aspect of the handling that Spitfire pilots both modern and historic would romanticise about, it's also what made the Spit harder to aim than more stable platforms ( note something being more stable does not make the Spit unstable) but certainly not very difficult, even English 'island monkeys' could shoot something down in a Spit.

 

Yes I have faith in Yo-Yo and ED to create a spectacular version of any aircraft, I hope they cannot be influenced to neuter or boost any aircraft, they cannot ignore anecdotal evidence if the end result of cold hard data is wildly at odds with it, when it comes to validating a Spitfire FM then it should be easy to configure an in game one to a modern day spec and compare.

I am in 7th heaven with DCS right now, absolutely fantastic warbirds and in VR :joystick: its the next best thing to the real deal, Crumpp's version of a Spitfire would not be.

 

to clear up any ambiguity here is a video explaining aircraft stability that I believe is the hymn sheet everyone is singing from.

[NineLine]

You only have to see the level of obsession with this particular topic this poster shows across the internet, we don't even have a Spit in game yet so why start this topic?

 

I see the level of obsession you few have with each other over the internet (some of you banned on a number of forums), I might have to experiment some day, and have Crumpp give me the text and I will post it for him and see how much the reaction differs.

 

I am going to let your post stand, but its a good example how you guys cant get over each other. Discuss the topic, dont discuss the person.

 

The Spitfire is coming for DCS World, I see no issue with this topic, no matter whether I believe the OP is right or wrong.

[bongodriver]

I see the level of obsession you few have with each other over the internet (some of you banned on a number of forums), I might have to experiment some day, and have Crumpp give me the text and I will post it for him and see how much the reaction differs.

 

I am going to let your post stand, but its a good example how you guys cant get over each other. Discuss the topic, dont discuss the person.

 

The Spitfire is coming for DCS World, I see no issue with this topic, no matter whether I believe the OP is right or wrong.

 

I assure you it's the message not the messenger.

[Crumpp]

I think he is trying to show what level of instability he believes it has

 

That is actually measured without much to argue. I am sure Yo-Yo will get things right.

 

JtD says:

 

If you have forgotten what I'm talking about I suggest you read this topic. It's not that long. And there's no innuendo. Just fact. The Spitfire at NACA was not tested with CoG 4.8 behind the datum as you've stated and 22.5 cm are not 11.3 inch as you've stated. The correct figures are ~7 and ~9. Why do you keep discussing this? It's not up to opinion, you've made a mistake and could be happy that you've learned something. Feel free to rant on if it helps you, but that's really all I'll say about this.

 

Why do you keep supposing?

 

Just work the math yourself.

 

.314*85 = 26.69

 

(-4.8-21.89)/85 = 31.4% MAC

 

 

.766 inch difference between the Moment and Arm Datum on the RAE load sheet and the LEMAC of the wing root used by the NACA.

 

9-.766 = 8.2

 

(-8.2-21.89)/85 = .354 x 100 = 35.4% MAC is the rearward limit of the Spitfire at 9 inches aft of the datum.

 

Let's check it against the RAE MAC...

 

-9.9-.766 = 9.1

 

(-9.1-21.89)/85 = .364 * 100 = 36.4%

 

Well, that is excellent agreement with RAE MAC at 9.9 inches aft of 36.3%. Less than 3% error which is probably due to rounding....

 

:music_whistling:

 

 

Modern Spitfire Mk IX are only approved with a restricted CG limits.

 

Maximum Total Weight Authorised: 3402 kg (7500 lb)

CG range limits 3.5“ to 7.0” aft of the datum point which is a stud on the

forward face of the firewall port side.

 

http://www.caa.co.uk/aandocsindex/29016/29016000000.pdf

 

CG range +3.5 in to + 6.39 in AOD. The datum is defined as the junction of the

centre line of Frame 5 and the horizontal datum line which is parallel to and three

inches below the thrust line. Its position is indicted by a plate on the fuselage side

near the fireproof bulkhead.

 

http://www.caa.co.uk/aandocs/22416/22416000000.pdf

[Yo-Yo]

You only have to see the level of obsession with this particular topic this poster shows across the internet, we don't even have a Spit in game yet so why start this topic?

 

No aircraft flew on rails, there were instabilities in the Spit with a rearward CG just like any aircraft, it's the Spitfires light controls that made handling those instabilities require a touch of finesse, the same lightness made handling those characteristics so easy, you can hear Al Pinner say as much in the video, you could pitch too much with ease, you could correct it with similar ease, as mentioned the lightness was 'desireable' in a fighter and is primarily the aspect of the handling that Spitfire pilots both modern and historic would romanticise about, it's also what made the Spit harder to aim than more stable platforms ( note something being more stable does not make the Spit unstable) but certainly not very difficult, even English 'island monkeys' could shoot something down in a Spit.

 

Yes I have faith in Yo-Yo and ED to create a spectacular version of any aircraft, I hope they cannot be influenced to neuter or boost any aircraft, they cannot ignore anecdotal evidence if the end result of cold hard data is wildly at odds with it, when it comes to validating a Spitfire FM then it should be easy to configure an in game one to a modern day spec and compare.

I am in 7th heaven with DCS right now, absolutely fantastic warbirds and in VR :joystick: its the next best thing to the real deal, Crumpp's version of a Spitfire would not be.

 

to clear up any ambiguity here is a video explaining aircraft stability that I believe is the hymn sheet everyone is singing from.

 

 

 

THis video replicates the well known mistakes in explaining stability. First of all, it mixes aerodynamic center where the lift is applied (as I use right term) and the aerodynamic focus where the INCREMENT of lift is applied. The difference is the same as for ship stability.

 

 

So, in some cases a stabilisator can create not negative but even POSITIVE lift and the plane, however, is statically stable because the increment of lift at the stab will override the moment from the wing.

 

The second mistake is the dihedral explanation. In any serious book there is a well known explanation: if a plane got bank sideslip begins and only due to the sideslip the plane gets recovering moment.

 

So, though the pitch movement can be isolated, the bank and yaw movements can not, that 's why we generally mention SIDE stability. This isolation in the video is a very serious simplification of the matter.

[Crumpp]

.766 inch difference between the Moment and Arm Datum on the RAE load sheet and the LEMAC of the wing root used by the NACA.

 

RAE aerodynamic data on the Spitfire says the aft CG limit is 2.638 feet from the LE of the wing root.

 

2.638ft *12in = 31.656in - 9in = 22.656 difference in the Leading edge distance to Aft limit in the NACA and RAE

 

22.65in - 21.89in = .766in

 

-.766 = 8.2

 

(-8.2-21.89)/85 = .354 x 100 = 35.4% MAC is the rearward limit of the Spitfire at 9 inches aft of the datum.

 

Let's check it against the RAE MAC...

 

-9.9-.766 = 9.1

 

(-9.1-21.89)/85 = .364 * 100 = 36.4%

 

Hopefully this will reduce the questions as to where the .766in correction comes from...

 

That is what is needed to align the RAE moment/arm datum point with the NACA LEMAC.

[bongodriver]

THis video replicates the well known mistakes in explaining stability. First of all, it mixes aerodynamic center where the lift is applied (as I use right term) and the aerodynamic focus where the INCREMENT of lift is applied. The difference is the same as for ship stability.

 

 

So, in some cases a stabilisator can create not negative but even POSITIVE lift and the plane, however, is statically stable because the increment of lift at the stab will override the moment from the wing.

 

The second mistake is the dihedral explanation. In any serious book there is a well known explanation: if a plane got bank sideslip begins and only due to the sideslip the plane gets recovering moment.

 

So, though the pitch movement can be isolated, the bank and yaw movements can not, that 's why we generally mention SIDE stability. This isolation in the video is a very serious simplification of the matter.

 

hey it's not my video, what you call mistakes I call simplifications, and I am trying to help out a guy who doesn't seem to be familiar with the topic, my firs instinct is not to go knuckle deep into the guts of aerodynamics.

it doesn't alter the concept of stability,

Edited October 21, 2015 by bongodriver

[Crumpp]

Well if I ever do I wont be concerned about it, everyone I know who flies them certainly have no reservations about it's capabilities, you'd be surprised just how close to the edge modern day Spits have been flown by some of the private operators, the BBMF are certainly more cautious.

 

NONE of the Modern Restoration Spitfire Mk IX are allowed to fly at the wartime CG limits.

 

The post war CG limits are restricted for a reason.

[Random]

How about we all let Yo-Yo do his own research? I think he might have done it before and might even have made flight models for DCS before!

 

I'm sure the spit will need multiple revisions after release but I'm also absolutely certain It's going to be the best simulation of any spitfire so far.

 

I think the problem here is some feel everyone expects the spit to be an Instawin Uberplane and have to show it wasn't. Others feel the former few forum nembers want it to flip on its back and explode the second you look at it. I'm gonna go out on a limb here but I think both groups are wrong ;)

[NineLine]

How about we all let Yo-Yo do his own research? I think he might have done it before and might even have made flight models for DCS before!

 

I'm sure the spit will need multiple revisions after release but I'm also absolutely certain It's going to be the best simulation of any spitfire so far.

 

I think the problem here is some feel everyone expects the spit to be an Instawin Uberplane and have to show it wasn't. Others feel the former few forum nembers want it to flip on its back and explode the second you look at it. I'm gonna go out on a limb here but I think both groups are wrong ;)

 

If I am flying it, it will indeed probably flip on its back and explode :)

 

<--- source of Spitfire instability ;)

[bongodriver]

NONE of the Modern Restoration Spitfire Mk IX are allowed to fly at the wartime CG limits.

 

The post war CG limits are restricted for a reason.

 

Why are they less restricted for earlier marks?

 

 

 

http://www.caa.co.uk/AANDocs/29100/29100000000.pdf

 

interesting to read that in the absence of proper Mk1 documentation they have used MkV examples instead citing that a Mk V is just a Mk1 with a Merlin 45

arguably Mk IX's were just MkV's with Merlin 66's etc etc

I think you will find they refer to the best available military certificates and apply accordingly, this really leaves much of the 'hard data' that gets thrown around here as somewhat redundant as some of it is clearly not the same data that official establishments use.

 

A note from one certificate for another mark

 

2.0 Basis of Approval

Approval of this aeroplane has been based upon previous satisfactory experience of the type together with published modifications and inspections. Any new modifications have been examined as applicable against the requirements of BCAR Section K.

 

http://www.caa.co.uk/aandocsindex/21880/21880000200.pdf

 

Really just shows that they will approve on the basis of safely demonstrated previous experience within the military and no restrictions are based on its civilianisation.

 

It does leave the CG limitations on the current MkIX's a little bit of a mystery though they are hardly radical impositions.

[bongodriver]

How about we all let Yo-Yo do his own research? I think he might have done it before and might even have made flight models for DCS before!

 

I'm sure the spit will need multiple revisions after release but I'm also absolutely certain It's going to be the best simulation of any spitfire so far.

 

I think the problem here is some feel everyone expects the spit to be an Instawin Uberplane and have to show it wasn't. Others feel the former few forum nembers want it to flip on its back and explode the second you look at it. I'm gonna go out on a limb here but I think both groups are wrong ;)

 

I really don't see where the instawin uberplane idea comes from, nobody is asking for that, simply resisting the other argument is not asking for that, I want an accurate spitfire vices and all, I just don't believe the alternative argument and have more than enough information toto satisfy me that the other argument is pure fantasy.

[Crumpp]

If I am flying it, it will indeed probably flip on its back and explode :)

 

<--- source of Spitfire instability ;)

 

 

LOL.

 

 

I think both groups are wrong

 

There is not "two groups" although I do not blame you for thinking that given the ferocity of the personal attacks made against me for raising this subject in the first place.

 

This is a matter of measured data, facts, and science. It is quantifiable and provable. Yes, Yo-Yo knows what he is doing.

 

The misconception from some the Spitfire's flying qualities "destroys" the aircraft is simply without truth. It just means the Spitfire for much of its envelope is sensitive to pitch change and requires double control input same as many modern unlimited aerobatic aircraft. It gives it the unique personality which makes it a Spitfire and helps to complete the dog-fighting picture of the design. It is something that adds realism and depth.

 

The Spitfire was one of iconic designs of World War II and its record speaks for itself. However, the artificially stable computer renditions of the past do not represent what it took to master the aircraft.

 

 

 

 

The longitudinal instability is just part of what makes a Spitfire a Spitfire. Those who mastered it, love it for dog-fighting. It was a rose.

 

All roses do have thorns and being unfamiliar with them leads to being stuck by them.

 

 

 

It is one of the most interesting dichotomies of aeronautical engineering. I am sure Yo-Yo will have fun with this one and turn out another great product.

[Crumpp]

bongodriver says:

I have more than enough information toto satisfy me that the other argument is pure fantasy.

 

Fantastic!

 

Submit this quantifiable data and lets examine it like adults. I have quantified and measured the argument I have presented. Let's see if we can do the same for your dissension.

 

I have shown the stability margin remains the same as the aircraft's AC and CG limits remain the same.

 

Show me it has changed.

[bongodriver]

Fantastic!

 

Submit this quantifiable data and lets examine it like adults.

 

Ok, heres some quantifiable data on the approval of full wartime CG limits on a modern MkIX Spitfire, sorry it takes me time, I don't have any of this stuff pre prepared to satisfy any obsessive campaign and I have to look it up in real time.

 

Conditions Affecting This Approval

This aircraft is fitted with modification 1335 which introduces rear fuselage tanks (only the upper tank is fitted to this example). The weight and CG limitations of the Permit to Fly should be revised to read:

9.2 Loading limitations

Maximum total weight authorised (normal) 3402 kg (7500 lb) CG range limits 3.5 inches to 10.5 inches aft of datum Maximum total weight authorised (overload) 4309 kg (9500 lb) CG range limits 3.5 inches to 12.5 inches aft of datum

Datum is defined in the Pilot’s notes and a plate on the port side of the fuselage.

9.5 Other limitations

At weights in excess of 3402 kg (7500 lb), gentle manoeuvres only.

 

 

http://www.caa.co.uk/AANDocs/17661/17661040100.pdf

[bongodriver]

Heres an interesting report showing how a MkV Spitfire with absolutely miniscule adjustment to the wartime rear CG limit had all the minor adverse conditions presented by instability cured.

 

http://www.caa.co.uk/AANDocs/21053/21053000000.pdf

 

5. Flight Test

The aeroplane has been flown by several pilots and the results collated under CAA flight test report reference FTR/6958Y dated 20 January 1989.

This report covered flight with the aeroplane ballasted to achieve four loading conditions, one yielding an aft CG of 8.85 inches AOD at 6389lb. The original aeroplane limits were 3.5 to 9.0 inches AOD at weights up to 7300 lb. At this aft loading it was found:-

1. that the aircraft would gently auto rotate into the 1g stall. 2. that above 3g a push force was required to prevent the turn tightening. 3. turning stalls required a push force as the aircraft gently auto rotated into the stall.

With the aircraft ballasted to 7.76 inches AOD these adverse characteristics were not present and since the aeroplane will normally be operating with the CG about 5 to 6 inches AOD the aft CG limit will b declared as 7.76 inches AOD and this will be stated in the Supplement to the Pilot Notes for G-MKVC.

The maximum speed achieved during these flight tests was 340 KIAS. VNE will be declared at this value although the original clearance was to 390 KIAS (450 MIAS).