RV8 aerobatic limitations

[jonnoboy]

I've been interested in the Vans series of aircraft for some time, particulary the RV8. I know it is cleared for aerobatics, but I was wondering what this specifically entails. Is the aircraft limited to specific manoeuvres or is it dependent on what it is tested for? Admittedly it is quite extreme, but could one start doing inverted spins, flick rolls etc (with negative systems installed, of course)? Also, what's the roll rate, and G limits?

Cheers

[S-Works]

Are you sure they are cleared for aeros in the UK?

[jonnoboy]

So I have been lead to believe. I don't think they've been cleared that long though!

[gasax]

Oh do keep up!

This might be a good place to start looking http://www.pfa.org.uk/Data%20Sheets/303%20VANS%20RV8.pdf and then the RVsquadron...

[stiknruda]

The PFA's aerobatic flight test schedule includes, loops, rolls off the top, stall turns and positive spins.

Inverted spins and flicks are intermediate competition figures - hardly extreme! Neither are particularly high G: neg one for the spin to commence about 4positive on the pull out. Flicking is about 3 pos or slightly less (in my aeroplane) negative - just very uncomfortable negative!

Inverted spin recovery is (Pitts-centric comment!) more rapid than erect recovery because whilst erect the tailplane blanks a large proportion of the rudder. Inverted it only blanks the lower section of the rudder.

[Mark 1]

The -8 has quite a good aerobatics envelope compared to the -4 with about 200kg typical load - two people plus a reasonable amount of fuel.
Surely, if you are allowed loops, rolls, stall turns and spins, then everything else is essentially a combination of those maneuvers.
Van's aren't very keen on flick maneuvres though they don't explicitly bar them.
There's a video of flicking a -4 on http://www.rv-4.de/video/G-Rolle.wmv

The -6 and -7 should be getting their aeros approval before too long.

Limits are as in the PFA document; expect a roll rate of about 150 degs/s.

Interestingly, the -4 is approved for 3 turn spins, but the -8 only 2.

[stiknruda]

Mark - are you sure that is a flick roll? It looks like a vanilla aileron roll - though I admit to not have flicked an RV4 though I have slow-rolled one!

Pitch up 30 degrees, check and stick over.

To flick it, you need to momentarily approach or exceed critical alpha, so that when the rudder is smartly applied after brisk rear stick, the inside wing stalls and develops zero lift. Smartly push the stick forward to unload or the roll component becomes buried.

[Flyingcircusace]

+6 -3 gives you scope to fly all the standard, and intermediate aerobatic figures. I am sure it will flick, but how heathly for this type of aircraft such a figure is, only time will tell. A fantastic touring aircraft that can swoop a few aero's on sunday, yes none better. Dedicated aero mount.....no, in my opinion of course.

As for the G loading, its not normally the aerobatics that overstress the airframe, but the recovery from bad aerobatics...................

Get trained.

RV are a fantastic series of aircraft that have done wonders for the homebuilt market, I am just glad Dick Van Grunsden was able to develop his designs in a regulatory system that worked with him, rather than against.

[Mark 1]

Stik - It's a German site, and he describes it as a "gerissene rolle" (clever roll?).

The airspeed on entry looks to be about 70 knots, which would be quite slow to get that roll rate with ailerons alone, and the pre-roll pitch-up could be consistent with a snap.
Its not a maneuvre that I've tried, so I'm guessing a bit

[DaveW]

The -6 and -7 should be getting their aeros approval before too long.


Mk.1, are you able to provide more info on this?

Last I've seen is information on the RVUK site regarding negotiations with the PFA. From what I'd read there, those had stalled (Ha!) due to, IIRC, PFA requirements for load testing of the tailplane and perhaps other components, which Van's weren't willing to go to the expense of (no real surprise!). Also UK spin testing. There was some discussion about some UK builders supporting the project, though - but this was around 2004.

Very interested to hear what's been happening recently.

[Mark 1]

The PFA have now issued permits to test an RV-6 and an RV-7a covering spin and aerobatic testing.
This will be performed by the same pilot who did the testing of the RV-8.
A combination of weather and availability has meant not much happening so far.
Successful completion of these tests, as I understandit, should form the basis for all other RV-6 and -7s to be put through the standard PFA aeros flight test and gain approval.

It's been a long time coming, but there does now seem to be light at the end of the tunnel.

Now, where's my rivet gun.....

[DaveW]

Thank you! And I had a very pleasant trip tonight in the Southwest, so that good weather is here, waiting for availability. :ok:

Now, where's my rivet gun.....

I'll have it after you :)

[stiknruda]

Mark,

the rotation rate and that fact that there was no massive acceleration onto the roll after pitch up causes me to still believe that it really is an aileron roll - 70kts after pitch up, by the times the wings go knife-edge the first time lift has dropped dramatically. As they go inverted with high alpha, they'll get a wee bit of lift and suddenly they are knife-edge with the nose slicing through the horizon, wings level - oh, look nose down......:E :E

notwithstanding the above - a sweet vid :ok: :ok:

[waldopepper42]

Not sure I'd want to flick roll a -4. If you look under the fairing near the vertical fin you will see that the mounting bracket for said fin is only slightly thicker than bacofoil!

Having said that, I'm in two minds - the initial g-force in the pull up (3g) is consistant with flick entry (and unnecessarily high for an aileron or ballistic roll), and there is a visible left yawing motion left just before the roll starts - again consistant with a flick roll....

I have experienced basic aerobatics in both the -4 and the -8 and they're both very pleasant and capable aeroplanes.

[henry crun]

waldopepper42: just as well you qualified that remark and told us it is the vertical fin, otherwise some of us might have confused it with the horizontal one. :ugh:

[air18150]

I am hoping to go for a ride in an RV8 soon. Its not an aerobatic competition machine, it goes too fast ! especialy, I understand if allowed to point at the ground for any time at all.

[waldopepper42]

Henry: Oops - now that I re-read it, it does sound a bit stupid, doesn't it?! :O :O :O
Sorry if I offended anyone else's intellect! :{

The point of the comment is still valid, though....

[Mark 1]

If you look under the fairing near the vertical fin you will see that the mounting bracket for said fin is only slightly thicker than bacofoil!

Waldo, I'm not sure I understand this. The fin attachment on the -4 and -8 are similar. The rear fin spar takes the direct rudder loads and is bolted to the fuselage through a 1"*1"x1/8"thick bracket made of extruded 6061 alloy (same material and section as the longerons).
The front spar, which I think you may be referring to, attaches to the fuselage via the tailplane forward spar through a .063" thick 6061 alloy plate on the tailplane and similar 1"x1"x1/8" extruded brackets to the fuselage.

While building, I've always been impressed by the design work that has gone into the RVs, they are very strong, generally elegantly designed, and well up to the g-limits and Vmc that Van specifies.

It is designed to take full rudder deflection at over 120 knots, stall turns and aggressive side-slips, all of which are likely to load that area more than a flick-roll.

Have you compared it with any similar aircraft?

[waldopepper42]

Hi Mark,

No - I haven't compared, it's just that to my inexpert eye, 0.063" doesn't look much!

Incidentally, if

"It is designed to take full rudder deflection at over 120 knots, stall turns and aggressive side-slips, all of which are likely to load that area more than a flick-roll"

is true, how come it's not cleared for flick rolls? Somebody, somewhere must have decided that there is some deficiency in the design that precludes them??

WP

[Mark 1]

WP,

As far as I know, you are allowed to do them. The limitations do not preclude them, even if they aren't specifically noted; so long as you don't exceed any operating limits.

Checking the manual, Van's specifically list the following maneuvers and entry speeds for the 8 and 8a:

Loops, horizontal eights 140-190mph
Immelmans 150-190mph
Aileron/barrel rolls 120-190mph
Snap rolls 80-110 mph
Vertical rolls 180-190mph
Split S 100-110mph

And, interestingly, they make the following note:

Because the RVs have good stall characteristics and good spin resistance, they also resist easy snap roll entry. Entered at speeds below 100mph they tend to be slow and wallowing. At above 100mph high G loads are required. For this reason most RV pilots avoid snap rolls and concentrate on looping and rolling maneuvers more suited to the performance and handling characteristics of these planes.

Or, as one colleague once put it; "it flicks nicely" is a euphemism for "it has a vicious stall".

There you have it. As I see it, flick-roll them if you want, but I probably won't bother.
Damn good fun aeroplanes nonetheless.

Mk.1

[foxmoth]

Snap rolls 80-110 mph

Actually allows a pretty fast entry speed for flicks - maximum entry speed in a Bulldog for example is 80kts (92 MPH).:eek:

[javelin]

Yes, but that's British Foxy :E

[waldopepper42]

Damn good fun aeroplanes nonetheless.


Absolutely agree! I have been lucky enough to fly in (though not as P1) Vans RV4, 6,7,8 and 9a, and they're superb aeroplanes. Didn't mean to criticise the mark, it was just the flick rolling bit that I had doubts about!

Thanks for the info, Mark - obviously a lot better informed than me :ok::ok:

[jonnoboy]

Anyone own one that would be prepared to show it off in the camridgeshire/east anglia region. Contribute costs of course!

Thanks for the great replies!

JB

[smarthawke]

jonnoboy

Couple of places to make contact:

RV Sqn through the Yahoo group:

http://groups.yahoo.com/group/rvsqn/


East Anglia RV society:

http://www.rvee.org.uk/

Also have a look at:

http://www.rvuk.co.uk/

http://www.rvforum.co.uk/YaBB.pl

It could be a very expensive ride.....!!

[AirScrew]

The PFA certification for -8 Aeros is 703Kg.

So Aeros with a P2 are permitted, subject to fuel and diets...Yes???

[Mark 1]

The factory introduced a revised (-1) wing kit in 2000 and allowed an increase in aerobatic (+6/-3G) gross weight from 1550lb to 1600lb (726 kg).
This increase hasn't filtered through to the LAA limitations yet.. I don't know why that is, as they are normally happy to go along with Van's recommendations. Possibly they want analysis or testing results to support the case.

In any event, a typical RV-8 comes out at 490-520kg empty. So add two 50th percentile adult males at 77 kg each and you still have room for 30-60kg (40-80 litres) of fuel without exceeding the limit for aeros. Typically CG will be in range too. Heavier engines and props will keep the CG forward but limit the payload, whereas lighter, wooden prop combinations may need to ballast the front baggage bay to avoid the rear CG aero limit.

If the LAA get around to accepting the 50lb increase in aero gross weight, then the option to take heavier crew and more fuel on dual aero sorties would make a useful difference.

[markkal]

SORRY, I am unable to space my text with paragraphs, don't know why...................... Hi folks!!!!! Seems that the whole discussion revolves around plain G load tolerances...Please consider the following; About flicks: What about torsional loads on engine mount ( in and against torque) and fuselage ??? No instrument to record them, definitely a primary consideration during design of an aerobatic machine. Increased loads ( Up to 50% as compared with the G meter loads recorded in he cockpit ) on the stalling side of wing during flicks.. Control surfaces; Rudder and elevator are deliberately oversized on aerobatic planes.. Excursion of these surfaces are also greater. Normal sized tailplanes will undoubtedly allow for a loop, though with a much greater radius, and would offer poor handling characteristics at low speeds.. The wings of an Extra or Sukhoi are fully symmetrical with no incidence, showing similar characteristics in upright or inverted flight. A different story with most experimentals or racers...look at the Cap 10, originally a nice tourer designed by Piel and improved by Mudry. Was born with nice oversized movable surfaces on the tail. But the elliptical non symmetrical wing with dihedral shows peculiar characteristcs during inverted flight, spins and flicks. The new Cap 10C carbon reinforced lower aspect ratio aerofoil had to be redesigned in some respects because of tendency to flick under negative dynamic loads... Think about a negative recovery ( -3G ) after a vertical dive with an RV, would'nt like to experiment that!!! Better have a Christen inverted system fitted to your plane if you don't want the engine to starve of lack of lubrication, with that red pressure lamp blinking !!!!!!! Better gain some experience with an aerobatic instructor... Wear a parachute Have plenty of room below ( Height )when experimenting Keep the entry speeds for flicks at 1,3 VS.... Remember: stall speed increases as the square root of the load factor. So don't panic if your butt feels some shudders during dynamic loads indicating a stall... just relieve pressure on the stick Remember also: When speed doubles the load factor, with same inputs applied, increases at the square root...e.g. 4 times !!!!! In an Extra or Sukhoi, with light control forces you'll find out real quick what I mean, but these machines have a great margin before reaching + or - 10G's Then structural limits are well above that 50% too 100% above. So study carefully your flight envelope and respect it !!!

[Thegoodshepherd]

I can testify that the RV6 will aileron/slow/barrel and snap (flick) roll
well - as Vans manual says its a manuever approached with caution
but it will snap nicely if entered at about 110-115 without loading up.
From talking to RV8 pilots its even nicer :ok:

the RV6 is a very nice little beastie all around - the one I did Aeros in
was half way through a "fly the borders" of the US by a then in-law.

Shepherd

[will5023]

Hi Guys, sorry to late reply on this one, yes theRV8,RV6 RV7 and 7A(nosewheel) are now cleared for aeros, reason I know this....I did the test flight for the RV7, as the LAA wanted a full spin test with the wheel at the correct end of the airframe:}, it does all the manuveres as mentioned, although I did not flick roll her at the time.

Will.