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Bob Grimstead
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Posted Monday, December 28, 2015 @ 11:17 PM  

Greetings Fellow Fournicators,

Spins have always fascinated me. I enjoy doing them, but you do hear an awful lot of bollocks being talked about them.
Some instructors and books will say 'One wing is completely stalled while the other is still flying'.

Things become worse when the subject of in-spin or out-spin aileron arises. 'If you apply out-spin aileron the downgoing aileron makes the inside wing even more stalled' (whatever 'even more stalled' is supposed to mean!) or 'In-spin aileron helps you to recover from a spin by reducing the outer wing's angle of attack and un-stalling it'.

People (often quite experienced pilots who should know better) seem to say these things because they presume (ie 'guess') that is what happens. But when you actually try these things in a Fournier, the aeroplane does not do what these theorists say it will. Out-spin aileron will very nearly stop a spin, while in-spin aileron helps it to tighten and flatten, rather than recovering.

These bar-room theorists (and most instructors) will also say 'Ensure your throttle is closed before attempting recovery from a spin, or the propeller's gyroscopic effect will prevent recovery.'
To which I say, "That is utter twaddle. The quickest way to get your Fournier out of a spin is the simultaneous application of full opposite rudder, full throttle and as much forward stick as necessary (about 75 per cent)."
How do I know this? I have experimented, and proved it many times.

Let me explain the terms 'in-spin' and 'out-spin' aileron or 'pro-spin' and 'anti-spin' aileron. If you are spinning to the right, in-spin (or pro-spin) aileron is right aileron (move your control column to the right), and out-spin or anti-spin aileron is left aileron.

Incidentally, if you do not very firmly and positively hold your stick central laterally, aerodynamic forces will blow it at least half-way towards the spin (ie in a spin to the right your stick will blow to the right of centre) so you are already getting spin-flattening in-spin aileron whether you wanted it or not.

Being of an enquiring nature, I thought I would actually find out what is happening on my wing during a spin with pro- and anti-spin aileron applied, so I tufted HDO's right wing and clipped a GoPro to the right canopy rail. To give further information on outboard angle of attack, I taped long streamers of wool to my wing-tip aerobatic sight.

Then I went spinning... thus:

To get decent quality viewing, tap/click on the three-dot icon in your screen's top right corner, then click/tap on the cogwheel, then click/tap on 1080. Without doing that the resolution is so low you can't really see what is happening.

No aileron:
http://youtu.be/hoR9hMOO0Lw

In-spin / pro-spin aileron:
http://youtu.be/DEhLq-W66bs

Out-spin / anti-spin aileron
http://youtu.be/oaHdL1Iw2_s

Enjoy.

Comments welcome.

Yours, Bob

[Edit by Bob Grimstead on Monday, December 28, 2015 @ 11:22 PM]

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Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

Roger.Camp
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Posted Saturday, January 2, 2016 @ 05:49 PM    YIM

Hi Bob,

"The quickest way to get your plane out of a spin is the simultaneous application of full opposite rudder, full throttle and as much forward stick as necessary"

This is what I was taught 45 years ago and hasn't failed me since and actually surprised the check pilot in Switzerland some years ago when on a check flight.

Happy New Year to you all.

Roger

[Edit by Roger.Camp on Saturday, January 2, 2016 @ 05:50 PM]

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SteveBeaver
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Posted Saturday, January 2, 2016 @ 06:17 PM    YIM

Try that in a YAK52 and you will die. Best to use the pilot's operating handbook.

Fredrik S
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Posted Monday, January 4, 2016 @ 05:44 AM  

In sweden where most people that fly TMG:s do it on their glider certificate (myself included) we teach our students to spinrecover in the same way as if you spinrecover from a glider and i think (not sure) that the PPL people are teaching the same thing.
No matter if you got in a spin with idle throttle or full throttle we teach them to recover by neutral stick, full opposite rudder and if necessary stick a bit forward.
As a glider instructor flying TMG:s i do not teach my students to fiddle with the throttle until after they have recovered from the spin.
I was told that we teach this way of recovery and that most PPL teachers in sweden teach the same because (apparently) fiddling with the ailerons (As in applying when recovering) when trying to recover can cause the spin to become worse rather than stopping it on some airplane models.

When spinning XSK i have never had to use forward stick to recover from a spin nor change the throttle from idle to full, she stops quickly and as she should with just neutral stick and full opposite rudder

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Best regards
/Fredrik Svanberg
RF4D serial#4104 SE-XSK

Martin Hill
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Posted Thursday, January 14, 2016 @ 06:39 PM  

Bob - enterprising indeed!

It would have been informative to see what the tufts do on the out-spin wing (or spin left) to address the "one wing is still flying" question.

I initially wrote a more detailed piece on spinning and Bob's findings but it was too long to post!
If you want to read all you can hopefully find the link below . I have added some to it.
Below is a "summary".

About spins
- A spin is predominantly, but not exclusively, gyroscopic.
- For straight winged aeroplanes it is usual to see a steep spin and a fast flat one.
- A flat spin is more stable and faster.
- It takes longer to recover from a flat spin than a steep one.
- Spins exhibit the gyroscopic phenomenon of inertia coupling (precession) - when a moment is applied around one axis one sees a resultant motion in another.
- Spin recovery uses this principle - not direct forces to oppose the motion.
- Pitching the aircraft down in the spin reduces the rate of rotation and increases the sideslip and leads to recovery.

This is the critical bit!
- The cross coupling (precession) seen in any one axis is dependant on the difference in moments of inertia of the other two axes.

Effect of aileron
- On most aircraft the yaw moment of inertia is greater than the roll moment of inertia.
- If the yaw moment of inertia is greater than the roll then the effect of in-spin aileron is to pitch the aircraft down - making the spin steeper and slowing the rate of rotation.
- Fourniers and gliders have long wings and a high rolling moment of inertia such that it remains greater than the yawing moment of inertia in all spin attitudes. This means that in-spin aileron will cause the aircraft to pitch up and the spin to flatten and speed up.

Effect of elevator
- Pitching down using the elevator couples into the roll axis in a pro-spin sense.
- The aerodynamics of a down elevator mostly reduces fin effectiveness and yaw damping resulting in a pro-spin effect.

Effect of prop.
- The effect the prop has on the aircraft will depend on its angular momentum (moment of inertia and rpm), the relative moments of inertia of the prop to aircraft along the aircraft roll axis and the distance of the prop from the aircraft cg.
- The precession caused by the prop is in pitch when the aircraft yaws and in yaw when the aircraft pitches.
- Propwash acts on the fin in the same sense as the precession.
- If the prop turns anticlockwise (viewed from the front) it will cause spins to the left to be flatter/faster and right spins steeper/slower.
- Increasing prop rpm increases the effect.
- Propwash over the fuselage, fin and tail will increase yaw damping and aid spin recovery.
- On most aircraft the negative effects of power are dominant when spinning with the prop (left for an anticlockwise).
- Power will help when spinning against the prop (right for anticlockwise).
- Use of power can overspeed the aircraft in the recovery.
- If your "spin" was actually a spiral you will most likely break the aeroplane!
- The Fournier the wooden prop has a low mass relative to the aircraft, its moment of inertia is small compared to the aircraft's roll moment of inertia (long wings again) and the prop - cg to wingspan ratio low(er) than "normal" powered aircraft so the precession effects may not be apparent.
- It seems likely from Bob's experimentation that, on a RF4 at least, the beneficial effects of propwash over the fuselage, fin and controls are overcoming the usually negative gyroscopic effects.

I hope this helps understanding but would reiterate Steve's comment - stick to the POH (unless you have the skill, confidence, height and aeroplane to allow some experimentation).

Remember though that the POH and certification are legalistic - they only guarantee recovery if you do what it says (and then not necessarily very fast).

This might now give you a clue why the POH says what it says.

Be safe and have fun.

https://drive.google.com/file/d/0B31AhYhUe13QTTR2S0RESjhXc0E/view?usp=sharing

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RF5 #5107 G-BEVO

Martin Hill
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Posted Thursday, January 14, 2016 @ 06:54 PM  

Fredrik

What you are teaching is absolutely correct. In accordance with FAR/JAR(CS) certification requirements the standard procedure to recover a glider/motorglider is as follows:
(direct quote)
Where applicable, close throttle.
Sequentially:
(1) Check ailerons neutral.
(2) Apply rudder opposite to the direction of the spin.
(3) Ease the control column forward until rotation ceases.
(4) Centralise rudder and ease out of the ensuing dive.

This does not apply to any other type of aeroplane and also doesn't mean something else might work (better even) in a glider/motorglider. It is just that this sequence must work and recover the glider within the required number of turns.

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SteveBeaver
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Posted Thursday, January 14, 2016 @ 07:52 PM    YIM

I think that aviators sometimes get a little carried away when discussing spins and recovery techniques. Erik Müller's "hands free" technique, in-spin aileron, out-spin aileron, throttle closed, throttle open or whatever. There are many opinions.

We sometimes forget that for certified aircraft at last we have a more or less coordinated "system" in aviation. In order to meet certification standards, an aircraft must demonstrate certain spin recovery characteristics. Those recovery characteristics are what instructors are trained to teach, and those are the techniques that appear in the POH.

Of course if you choose to fly an experimental aircraft, or if you choose to operate a certified aircraft beyond the limits specified in the POH, all bets are off.

For the most part though, "by the book" is the right approach.

Bob Grimstead
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Posted Saturday, January 30, 2016 @ 08:03 AM  

Fournier RF4D spinning

Hi again Martin,

It is such a pleasure to hear from somebody who really does know what they are talking about when discussing spinning. I am so grateful for your detailed reply.

Incidentally, to make a long post on here, simply type it up in your preferred word processing program, and then copy'n'paste it bit by bit into sucessive posts, as I have done here.

Thank you very much for your extended explanation, which I am ashamed to admit I have only just fully read (because of more urgent recent family issues).

Despite having learned aerodynamics to Hamble's ATPL level, very extensive reading around the subject and much experimentation over the years, I have learned a great deal from just a single reading of your treatise. I hope to glean much more on subsequent re-readings.

It is good to hear your expert assertion that 'There are no generalisations when it comes to spinning, all aeroplanes are different.' That is what I had long suspected. Indeed, this is clearly even true of different examples of the same type, for those who know anything of the spinning accident histories of Tiger Moths, Stampes, Chipmunks and Tomahawks, to name but a few.

I shall soon re-tuft the wing and make a number of spins to the left to see what is happening out there on the outer wing.

Considering your mention of a ninety-degree Angle of Attack, presumably this refers to a semi-span or semi-half-span average. It is interesting to see that the inboard wing-tip AoA on my clips clearly exceeds 90° in all my spins, although it is unlikely to be that much at all semi-spanwise stations.

From the start I want to make my original intent clear.
I want to begin a display with the flattest possible spin (greatest number of turns for a given height loss) but of course to be certain of recovering in a predictable number of turns (preferably, but not definitely, quite promptly). Many display pilots do this in other types, but I feel the RF4's long wings and wingtip smoke would make the resultant 'double helix 'a pleasing spectacle.

My experiments (I have made many spins) confirmed your statement that in-spin aileron causes an RF4D to pitch up a little and spin slightly faster and flatter, while power-off recovery is still quick (around three-quarters of a turn) and uses no more measurable height than from a spin with centralised ailerons.

My spins were deliberately all made with a central Centre of Gravity.
I understand that an aft CoG 'normally' results in a faster, flatter spin. Were I to experiment with an aft CoG to get a flatter display spin, I would obviously do so very progressively, and with loose shoulder straps and possibly a moveable heavy weight in the cockpit with me to get the CoG forward again in extremis (and wearing a parachute of course).

Presumably having smoke canisters in the smoke pods will increase my roll moment of inertia?
Other modifications to my RF4Ds include aileron gap seals (as recommended by BAe's John Gibson and definitely improving the Fourniers' low-speed roll-rate).
I shall probably fit rudder gap seals too, for improved low-speed effectiveness, which I now understand might not be as important as I had previously thought in spin recovery.
The unusually long fuselage helps greatly.
René made a very good job of designing the tailplane/fin/rudder geometry too, although for extra spin recovery effect I've long toyed with the idea of a large fixed (but lightweight — flutter) trim tab on the rudder's rear apex, giving it the lower area of a Zlin's or a CAP 232's.

The American translation of the RF4D's Flight Manual says of 'normal' spin recovery: Spins is allowed, recovery by normal procedure. and...
Recovery:- apply opposite rudder- ease stick forward- ease out of dive.

You mention 'Certification Requirements', but these are presumably 21st Century EASA requirements. Were 1970 French requirements the same (ie no combination of power and controls will render recovery impossible)?

Given that a VW rotates clockwise as viewed from the front (opposite to your example) Fournier spins to the right should be flatter. Flatter still with increasing amounts of power, and even more flatterer with an aft CoG.
The thing is, will it recover predictably?
I suspect it will, because its handling is so exemplary in all other circumstances, but careful, gradual, step-by-step experimentation will reveal the truth.

I know from experience that, with an approx 40kt spinning speed and a 135kt Vne, using power will not cause an overspeed or overstress during even a competition recovery with a prolonged down-vertical.

[Edit by Bob Grimstead on Saturday, January 30, 2016 @ 08:14 AM]

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Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

Bob Grimstead
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Posted Saturday, January 30, 2016 @ 08:09 AM  

I use very light propellers (Heliptera in Australia — temporarily, and Hercules in England) with very low engine idlng speeds, so presumably their gyroscopic effect on spinning is minimal, and beneficial compared with the heavier original Hoffmann props.

I would be very interested and extremely grateful to,hear your further thoughts on any or all of the above Martin.

Finally, I would love to know what modification you made to your RF5 that required spin tests — athough Francis always seems to want extensive spinning tests for even the fitment of a cockpit cup-holder, presumably to scare away all but the hardiest potential modifiers.

Yours very gratefully, Bob

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Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

Martin Hill
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Posted Tuesday, February 9, 2016 @ 07:02 AM  

Hi Bob
First I hope the family issue you mentioned already in your email hasn’t been too stressful and second sorry for not noticing your post sooner.

Answers in order:
“Even same types can be different” – yes. Example, Tiger Moths and Chipmunks can have “spin” strakes or not. Completely different deal. Notably all RAF basic trainers from the Tiger through to the Bulldog have been fitted with these. They make the spins more consistent, stable and recoverable. So when Wing Co Toff tells you, whilst propping up the local flying club bar, he knows everything about spins, he doesn’t. He’s only likely to have experienced something that has been nicely engineered for him.

You mention the Tomahawk. This is an interesting case. Its general configuration (yes a T tail) should make it good for spin recovery. It has a particularly poor stall/spin fatality record not because it is a bad aeroplane but because the people who jump into them are inadequately trained and briefed. It’s not the C150 or PA28 they learned on (and probably didn’t spin either).

Gliders, almost by design should spin and recover the same. The Puchasz has a similar reputation to the Tomahawk in this respect and in truth you wouldn’t want to spin one below 1000ft unless you got onto it pretty quick and give it absolute full controls. The POH does and any decent instructor should warn of this. Again like the Tomahawk and every other type of aeroplane- - read and do what’s in the POH.

Ninety degree AoA – meant at the cg. Along the wing you have all sorts.

Your intent – not sure what you are wanting to achieve here, as anything that makes a spin flatter will also make it slower to recover. I guess you are looking for a trade-off.

CG – yes aft cg will give the flattest spin. The deal with certification is that the aircraft must be recoverable at the most aft cg. It sounds like you might have read that tosh about an F16 pilot who recovered from a spin by undoing his straps and leaning forward to shift the cg! No loose/moveable objects, including yourself please. I suggest carefully work out what load gives an aft cg and go try or work towards. As long as you stay within the limits you will be fine.

As the cg goes aft recovery will start to take longer. Maybe not what you want for a display.

I seriously doubt that one can do anything aerodynamically (use of power, ailerons, whatever) that will put a Fournier into an unrecoverable mode (cg in range of course). However breaking it is an entirely different matter.

Smoke cans – don’t know how much they weigh, but yes they will increase roll moment of inertia and proportionately less the yaw MoI. They will also contribute to yaw damping. It is difficult to know exactly what the effects are without the numbers but the cans are likely to increase the aileron effect although they may be also slowing the spin down slightly.

John Gibson – for two years, just over four decades ago, in my first proper job, I sat next to John. A very talented, quiet and gentle man. Massively enthusiastic glider pilot too (not my thing at the time).
Not sure what you were trying to achieve and whether John’s advice was specific or general.
To explain – most modern gliders have a laminar section. They also tend to have quite poor control surface hinge designs. Using tape or seals keeps the flow better attached, reduces drag and improves control effectiveness. Gliders also tend to operate at lower Reynolds Number. It means the flow is much less stable and likely to separate.
In normal flight the flow over a Fournier outboard section is always turbulent and therefore more likely to stay attached.
A change made from the RF3 to the RF4 was shrouds over the hinge gaps. An RF3 will definitely benefit from seals over the gaps, even if it’s just tape, although you are still left with a discontinuity in the surface – but it’s better than air flowing through it.
Generally it is better not to seal shrouded gaps, particularly if there isn’t a shroud on the underside of the wing. What is going on here is that air is allowed to flow from the high pressure lower surface and out of the slot on the upper surface, in effect blowing the surface (like a slat) so keeping the flow on the aileron attached.
I have no idea what Rene or Alfons intended but it might be cleverer than first appears.
However, if you have tried it and it improves control effectiveness then fine. Stops water running through as well!
I presume you are using the Mylar strip stuff.
So seals on gliders, yes (in fact on some they are essential to prevent surface flutter) on Fourniers, doubtful, or they would have become standard by now.

...cont

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RF5 #5107 G-BEVO

Martin Hill
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Posted Tuesday, February 9, 2016 @ 07:04 AM  

Tab on rudder – absolutely not. You would be treading into dark areas of flutter, hinge loads and more. Francis will put you through the hoops. FYI some guys wanted to put a fixed tab on an RF5 elevator. Francis wanted all the calcs and a flutter flight test progamme. They gave up.

Certification – Don’t know what the original French spec says. The RF3, 4, 5+ were certified by Putzer to LBA Mitteilung 10.05, which was the basis for JAR now CS-22. However there are differences e.g. reserve factors. I’ve tried a few times to get a copy without success. Maybe if anyone has one it would be interesting to compare.
One oddity is that none of the Fourniers or a G109 comply with the definition of a motorglider by virtue of wing loading. Weird.

Prop – I doubt the kilo or so between a Hercules and a Hoffmann will make any difference particularly as a lighter prop will shift the cg forward, so the effects will probably cancel.

My mod – an engine change from 1700 to 2180. Spinning was a Francis tick box exercise. It’s on the standard list so do it or accept a permit limitation. Most of the other stuff was irrelevant as well.
A cupholder I think is a minor mod so he probably wouldn’t insist, but may depend on how big the cup is. He will want stress calcs for sure.

I am not bothered about spinning, I just love my Fournier, so I prefer to go break someone else’s aeroplane when doing this sort of thing.

Martin

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RF5 #5107 G-BEVO

Bob Grimstead
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Posted Tuesday, February 9, 2016 @ 07:22 AM  

Thanks Martin,

I had anticipated the rudder tab's flutter issue, but not the hinge loading.

Yes, nowadays Francis seems to want comprehensive spin tests for everything — presumably mostly to dissuade mod applications, since he currently has ?800+? outstanding, including half-a-dozen or more of mine for more than two years. And I only applied because most of those mods were already on the aeroplane when I bought it, nearly a decade ago!

If only we could persuade the CAA that Fourniers are not SLMGs or TMGs on that wing-loading basis!

Won't a lighter prop shift the C o G aft? 😉

Thanks again, Bob

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Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

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Posted Friday, February 12, 2016 @ 08:59 AM  

Yes of course. A lighter prop will shift the cg aft. I think I started on a different track - a heavier prop, on a Fournier, might make spins to the right flatter, but the more forward cg would steepen the spin ans reduce spin tendency.

Not sure why one would want Fourniers not be classed as SLMGs/TMGs. I seem to recall Rene's logic of going down the motorglider route was relaxed requirements e.g. only one magneto necessary, which enabled weight to be saved.
I know some airfields ban SLMGs e.g. Hawarden, but then they ban taildraggers as well. But then the place is run by two guys called Elf and Safti ergo Airbus.
Perhaps you have some other reasons.

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Bob Grimstead
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Posted Sunday, February 14, 2016 @ 06:47 AM  

Once upon a time, in the Good Old Days (and indeed in Australia and most of the rest of the World to this very day) Fourniers were simply aeroplanes, so anybody could fly them or learn to fly in them, with no need for a special rating, flight test, sign off etc.

And indeed, that is precisely what they are: delightful, sweet-handling, high-efficiency aeroplanes. They have no tricky handling issues, they don't require any particular skills to fly. There is absolutely no need for some idiot in the CAA to have deemed that they come into the same category as a VW-powered Falke or an HpH jet Shark etc.

As things currently stand, I can't let any of my friends fly my Fournier unless they go through the expensive process of ontaining a TMG Rating and, while on paper the rating itself only costs, what, £180, in reality they have to make familiarisation flights with an instructor in his expensive two-seater (Grob 109 or whatever) and then take a flight test with an examiner. As Matthew Hill discovered, the total cost of all this is more than £2,000! Just to fly a mate's little VW-powered aeroplane!

This is just plain ridiculous.

In the Tiger Club in the eighties, flying our Fournier merely involved a briefing and then lifting it on to trestles so that the prospective new pilot could put the wheel up and down a few times. Then off he or she went, in the club's cheapest aerobatic aeroplane.

Happy days, unencumbered by the CAA's usual heavy-handed bureacratic interference.

Yours, Bob

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Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

Donald
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Posted Sunday, February 14, 2016 @ 10:17 AM  

Bob,

Since this is an American forum but with a world wide appeal there may be those unfamiliar with British and European bureaucracy so I'll relate my experience.

I'm British so back in the day before EASA my PPL was issued by our CAA and came with a number of things. One was a SLMG rating (no such thing as TMG back then) but to maintain it I would have to have experience of SLMG flying in the first and every subsequent year I wanted the rating to remain. I didn't do that so effectively lost the SLMG rating.

But it also came with considerable liberty which meant that I could fly ANY single engine aircraft up to 5700 kg MTOW and that included retractable, variable pitch or CS prop, even turbine! Had I been rich enough I could get hold of an ex-service Gnat or L-39, jump in and go fly. Might not have been wise but it would have been legal.

What changed in Britain was, of course, the superimposition of EASA where, seemingly, every minor bureaucrat from the 29 states with an empire to build stuck their oar in and everything changed for the worse. General and light aviation was regulated as though it were CAT and a rating or 'differences training' was required for anything remotely different to what we trained on, but that freedom of my original PPL is what I exploited when I first climbed into what would become my RF3. It was single engine, was less than 5700 kg, off we go! Eventually, post EASA when Fourniers became TMGs I would claim TMG rights based on experience plus retract too.

So with the exception of blaming our CAA I fully agree with what you write that to differentiate the type(s) is to do them a disservice for in just about every variable you might imagine they are more forgiving of error and incident than the C152's and C172's I was mostly experienced in as well as other common training and club types.

Lastly, I imagine that since the deadline for having to switch to an EASA licence to fly an EASA type keeps getting pushed back, I think it's now April 2018, anyone in Britain still flying with the original 'poo' brown PPL ought to be able to exploit the same freedom I did twenty years ago.

Donald

[Edit by Donald on Sunday, February 14, 2016 @ 10:22 AM]

Bob Grimstead
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Posted Sunday, February 14, 2016 @ 10:59 AM  

All that you say is correct Donald, except that this silly differentiation of Fourniers from 'ordinary' aeroplanes was brought in by some idiot in the CAA, long before EASA or its predecessor JAA were even postulated!

Yours, Bob

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Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

Donald
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Posted Sunday, February 14, 2016 @ 12:53 PM  

Hi Bob, but was it not started with the French authorities, the DGAC, when they initially questioned René's insistence on single ignition and was it not then the compromise of a different classification that allowed his wonder machines to be allowed?

Donald

Bob Grimstead
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Posted Sunday, February 14, 2016 @ 01:02 PM  

That was a quite separate certification issue back in the late sixties.

This is a licencing issue brought in in the late eighties.

--------------------
Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

Bob Grimstead
Captain

Gender: Male
Location: Perth, Western Australia or West Sussex, England
Registered: Dec 2006
Status: Offline
Posts: 2027

Click here to see the profile for Bob Grimstead Visit http://www.redhawksduo.co.uk Send email to Bob Grimstead Send private message to Bob Grimstead Find more posts by Bob Grimstead Edit or delete this message Reply w/Quote
Posted Thursday, November 14, 2019 @ 08:17 AM  

Hi again fellow Fournier fliers,

Particularly the 'spinners' among you.

Here is a very interesting treatise on spinning which uses a T67 — which is really, aerodynamically, an overweight Fournier RF6B.

Happy reading...

https://bura.brunel.ac.uk/bitstream/2438/10537/1/FulltextThesis.pdf

[Edit by Bob Grimstead on Friday, November 15, 2019 @ 00:06 AM]

--------------------
Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

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