Spin testing observations - feedback requested

Hi,

Last week I did some spin testing on VII (RV 7A - large rudder) as part of the later stages of flight testing. I've been comfortable with the stall / power on / off / bank etc for a while and slowly worked up with 1/2 turn, 1 turn, 1.5 turn and 2 turn spins. First observation which I was expecting from the reading was 2 turns starts to really wind up - quite 'exciting' . That said it all did what it was meant to and responded nicely to standard recovery.

A short video of the stalls / spins - http://www.youtube.com/watch?v=xVMWKFI9gb4 - excuse the lack of music / my chatting - it was for flight testing!

I'm initiating with full aft elevator and full left boot at 60 kts in a slight nose up attitude. 1 turn seems to be about 400 feet.

Yesterday I also did some more .5 and 1 turn with more foreward CofG ( 1428lbs @ 81") . It seems to my limited experience to swing through even further to quite an 'inverted' position - is this others experiece too? The swing through is more than I was expecting.

As an alternative - if you have google earth installed ( http://earth.google.com ) a mini animation clip at 10msec is available at http://www.rvproject.gen.nz/kml/ZK-VII_2turn_spin.kmz - this shows nicely the attitude changes.

Hope to get feedback from others experience - particually the initial 'inverted / on the back' attitude before I start moving the CofG further aft towards the aeros aft limit.

Regards,

Carl

Based on the video, looks like you had enough after the 2nd turn.

How did the GRT avionics hold up during the spins? Any problems?

Jim

Hi Carl,

I'm no great expert but I do practice spins every couple of months (around oil change time preferably). From looking at your video your spins look identical to the view I'm used to seeing from my 7A (with the later rudder).

Looks like you are doing a good job on your flight testing.

GRT good

Jim P said:

Based on the video, looks like you had enough after the 2nd turn.

How did the GRT avionics hold up during the spins? Any problems?

Jim

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GRT goes great - no problems - that is what is providing the raw data for the google earth rendering The 'next generation' GRTDecode will be improved (when I get a few spare weeks.....)

2 Turns - enough for one day - then went onto some loops and rolls

Spins

kevinh said:

Hi Carl,

I'm no great expert but I do practice spins every couple of months (around oil change time preferably). From looking at your video your spins look identical to the view I'm used to seeing from my 7A (with the later rudder).

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Good - have you tried forward vs aft CofG - any differences? Next spins need to be further aft and I'm just being cautious....

kevinh said:

Looks like you are doing a good job on your flight testing.

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Thanks - any day for flying is a good one. Still working on temps but I think part of it is me expectin too much! I have learnt lots about delta pressures across the engine and have instrumentation for it and the various mods I'm trying.... another thread another day.....

Carl

Looking Good!

Hi Carl,

Your spins look a lot like what I saw in the -8 during my own phase 1 testing - I haven's spun a -7 myself, but they seem pretty close from your video.

Your program looks like it is progressing well, and should be an example for those folks who think that Phase 1 is "flying the same hour 40 times". The combination of GRT-recorded data, video, and voice recording sure makes it a lot easier to build a database than having to do it with pencil and paper, doesn't it?!

I wish I'd thought of mounting a camera like that during my own Phase 1, but the video camera I had at the time would have taken some engineering time - if I'd had the little SD400 I have now with a big memory card, it would have been a piece of cake, and I'd recommend that to anyone - do you have a picture of your camera mount you could share? I'd like to have that for my Flight Advisor files.

Congrats, and keep up the good work!

Paul

Questions

Ironflight said:

Hi Carl,
Your spins look a lot like what I saw in the -8 during my own phase 1 testing - I haven's spun a -7 myself, but they seem pretty close from your video.

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Does the 8 go on it's back too? any CofG changes?

Ironflight said:

Your program looks like it is progressing well, and should be an example for those folks who think that Phase 1 is "flying the same hour 40 times". The combination of GRT-recorded data, video, and voice recording sure makes it a lot easier to build a database than having to do it with pencil and paper, doesn't it?!

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We are basically finished with phase one - I can sign out the flight testing when I'm ready, but currerntly still playing with the cowl inlets / cooling. It becomes significantly more difficult for that type of maintenance once it is a 'fully fledged aircraft' in NZ so I'm holding back a little. The actual flight testing has been pretty smooth / easy, the 25 hours would have been plenty, but with the oil cooling problems early on and air inlet development work that has meant we chewed quite a few hours quickly - nearly time for a 50 hour check! We also had a couple of hours of X-country partly just to stretch the legs and learn a bit more about the systems. My piloting confidence has increased along with the confidence in the aircraft - very much a 'growing phase' in all ways.

The GRTDecode stuff has been great (when I remember to start and stop it!), hopefully GRT will get the auto start / stop logging working soon. GRTDecode needs quite a bit of work, I've started with development of a proper GUI and the Google earth representation will improve in the next version. I'm currently using quite a lot of Excel charting / plotting functions, it would be nice to integrate that too - but difficult to make flexible enough for everyone. I'd also like to be able to keep a continous timeline of the plane, rather than just a single flight. The FADEC engine log is great - provides complete engine history from hour zero and has helped in the diagnostic process more than once. Biggest risk for us is too much information and worrying about 'normal' things......

I still find logging on a knee pad the first cut of the information - things like % power, DA and TAS aren't trival to re-calculate and it is simpler to record with pen/paper and voice on video.

Ironflight said:

I wish I'd thought of mounting a camera like that during my own Phase 1, but the video camera I had at the time would have taken some engineering time - if I'd had the little SD400 I have now with a big memory card, it would have been a piece of cake, and I'd recommend that to anyone - do you have a picture of your camera mount you could share? I'd like to have that for my Flight Advisor files.

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Video - something I wanted from the start, the biggest problem has been audio - the camera has auto gain on it and overloads very easily. It is wired to the passenger lines on the GMA340.



The photo above shows the tray/bracket it sits in - there is a location peg on the bottom and a screw upwards to hold the camera down. The base pivots at the back and fixes at the front which meant the sky / panel can be adjusted. It works quite well even with two people. I'm using just a basic Canon DV camera, but seems to hold up to at least 4 G . The 43 hours of flight testing, most have been video'd - about 400GB of raw footage. I'll try to get a photo of it with a camera / more details for you when I'm next down 'big shed'.

Regards,

Carl

Nice video and thanks for taking the time to create, edit, and share.

What kind of speeds are you seeing in the recovery??

Thanks

Speeds

grantcarruthers said:

What kind of speeds are you seeing in the recovery??

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I think you can hear me calling them and the Gs on the pull outs. From top of my head 130 ish knots and 3 G from the 2 turn spin. It was slower than I feared, I'm sure nose down it will pick up quickly, but it was a simple, stick center, oposite rudder, count 1, roll stopped, pull gently (already in the 90+ kt range), wait for the horizon / positve climb / attitude, add power.

Not sure I'd want to spin power on! I'm guessing right boot might be a little more exciting too....

Carl

zkvii said:

Good - have you tried forward vs aft CofG - any differences? Next spins need to be further aft and I'm just being cautious....

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I don't regularly do spins at the forward and aft limits, but I did do them back in my phase one. I don't recall the differences - to me they all seemed quick but recoverable using the regular technique.

My recent stuff has just to stay current in case I botch my beginner acro moves.

Spin video

Nice video; thanks for the effort to do it and post. I wasn't able to keep track of all pitch changes leading up to the stall break or spin entry, so my impressions include some guesswork. I think the tendancy to go inverted in the first half turn may come from forcing the entry a little - i.e. hitting full rudder before the stall break has allowed the nose to "break" the horizon. Sometimes there is a natural input to increase AOA just before or at the time you expect a break to occur, producing a slight accelerated stall. This seems to be associated with a more vigorous entry and more initial roll. In IAC competition you are downgraded for this type of entry. Judges like to see the nose break through the horizon before any turn or rotation occurs. Trying this in the RV-8 owned by Wendell Foltz (delaying rudder input until nose has passed thru horizon) resulted in smooth gentle entry with no tendancy to go inverted. Try that and see if it yields a different entry. By the way, it ooked as though those two turn spins went more than two! Thanks again and keep us informed on spin behavior at various CG's and weights. Bill

spin vs snap

Carl,
I spin my 8 on a regular basis. I have also spun a 6 and 6A.
The primary reason you are rolling inverted on your spin entries is because you are initialting the spin prior to the stall, almost a snap roll. If you wait until the buffet (I realize there is very little) or the break, you will not roll over the top as you have been.

Scott A. Jordan
N733JJ
725 hours

Spin entry

Bill Dicus said:

I think the tendancy to go inverted in the first half turn may come from forcing the entry a little - i.e. hitting full rudder before the stall break has allowed the nose to "break" the horizon. Sometimes there is a natural input to increase AOA just before or at the time you expect a break to occur, producing a slight accelerated stall. This seems to be associated with a more vigorous entry and more initial roll.

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OK - that would sort of tally. I've actually got quite a lot of specific data from the GRT but it is difficult to really visualise it. The google earth render is pretty detailed - the attitude info is very accurate, the GPS lat/long and movement suffers from only being 1Hz (alot of movement in 1 secs)

Bill Dicus said:

In IAC competition you are downgraded for this type of entry. Judges like to see the nose break through the horizon before any turn or rotation occurs.

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So competition entry is? from the nose level with horizon with rudder netrual and as through the buffet and as a wing starts to drop, then rudder? Or starting with a more nose up attitude?

N733JJ said:

The primary reason you are rolling inverted on your spin entries is because you are initialting the spin prior to the stall, almost a snap roll. If you wait until the buffet (I realize there is very little) or the break, you will not roll over the top as you have been.

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Thanks Scott, I tried one yesterday at 55kts but was well forward CofG and seemed to be worse - hence some of the questioning..... What speeds are you using in the 8?

2 Turn - is 2 turn until initiating recovery, ends up being about 2 2/3.

Thanks for the input,

Carl

Spin video

http://youtube.com/watch?v=rK5DiNyEuzQ

This one shows a 5.5 turn upright spin in a 7a with large rudder...Oh and opposite aileron to provoke it a little.

Frank

Nice video, thanks. Looks like you went negative g on the last recovery(?) Was that the low oil pressure annunciator that lit up?

Christmas tree lights

fl-mike said:

Nice video, thanks. Looks like you went negative g on the last recovery(?) Was that the low oil pressure annunciator that lit up?

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Hi - not sure which lights went on, but probably EIS (red on the LHS) (oil or fuel pressure). The other possibles are in the center locations fuel pump (FADEC auto for low pressure), Mute light would be on for the AoA disable, MFD alert for EIS also, GPS possibly just as a airspace alert. I think it was only transitant - could have been fuel sloshing around causing min fuel on the EIS.

Just looked at the logs, Oil pressure went from 69 psi to 37 psi during the 2+ turn spin just after getting to a low of .2 G. Fuel pressure was pretty stable at 36 psia the whole way through just on engine pump.

Carl

Competion spins

I too, generaly do "competition spins". A normal unaccelerated stall and full rudder just as the nose drops. I'm not looking at the speed (and it would be different for every plane due to instrument and installation errors anyway) but the AOA is screaming "ANGLE, ANGLE, PUSH" just as it did in your stalls on the video. The fun part is pushing to the viertical down after the spin and adding full power to set up for the next manuver (1/2 Cuban in Primary).

P.S. I forgot to compliment you on the video. Well done and it can be used to help ease the anxiety of others exploring spins.

Scott A. Jordan

Hard to tell exactly from the video, but if the AOA is too loud there is a volume control potentiometer in the AOA box...

Nice video, spring is here and the smell of spins is in the air again!

AoA

N733JJ said:

P.S. I forgot to compliment you on the video. Well done and it can be used to help ease the anxiety of others exploring spins.

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Thank you - and you are welcome. I know I watched Dan C's spins before doing this and it helped get some idea of what to expect. Spins in themselves aren't a big problem - it is all about preparedness, practice and training IMHO.

MCA said:

Hard to tell exactly from the video, but if the AOA is too loud there is a volume control potentiometer in the AOA box...

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Hi Mark - yes the AoA is 'believably loud' as opposed to 'unbelievably loud' It cuts through everything, radio / ICS etc nicely though. The video audio levels as mentioned previously also overload a bit quickly.

Regards,

Carl

When I competed the judges liked to see level flight with slowly increasing pitch attitude (AOA) with no turn or bank until the nose drops through the horizon as the stall occurs; only then should rudder be added (maybe a little aileron to help begin roll) to initiate the spin. Use rudder and aileron as necessary to keep heading stable until the nose drops through the horizon. Resulting entry usually seems gentle. Forget the GRT and look outside the airplane. Hope this works for you. Bill

Spin entry

Bill Dicus said:

When I competed the judges liked to see level flight with slowly increasing pitch attitude (AOA) with no turn or bank until the nose drops through the horizon as the stall occurs; only then should rudder be added (maybe a little aileron to help begin roll) to initiate the spin. Use rudder and aileron as necessary to keep heading stable until the nose drops through the horizon. Resulting entry usually seems gentle. Forget the GRT and look outside the airplane. Hope this works for you. Bill

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Thanks Bill - that is plan for next time - I'll let you know how I get on. Outside - everything is outside - until I want to see the airspeed for pulling up.

Carl

Set the pitch picture for the stall then keep feeding in elevator until full aft, the rudder to maintain directional control and start feeding in the direction of the desired spin so that the spin begins at the full aft stick stall not before (as others have pointed out) After the spin starts you can neutralize the rudder but not the aft stick or the spin rate will accelerate. Keeping the stick full aft will keep the spin rate down until you are ready to recover.

Thanks for the help guys - had another quick blat yesterday, definetely slow entry although the accelleration or the spin seems to get to about the same speed after 1 turn.

Wonderful evening to fly - blue sky, sunshine and the autumn ('fall') colours of Central Otago. http://www.youtube.com/watch?v=T9XepriQ69o

Carl

Spins

Good going. Bill

spin will speed up

IF you put in full opposite aileron...

So full aft stick, full rudder and full opposite aileron...but keep it all the way back.

The snap rolls will go over a bit quicker using this method too..

Its fun!..

Spins

Frank: Haven't enough experience with RV spins - in most aerobatic aircraft outspin aileron causes flattening of the spin. In the Pitts (and many other acro mounts) this slows rotation rate and raises the nose relative to the horizon. Adding full throttle and (in a left spin) putting the stick in the right forward corner yields a fully developed flat spin. In the Pitts the nose comes up to a little below the horizon, the airplane gets quite "flat" with virtually no roll but high yaw. This can approach 400 degrees per sec. The contrary situation, i.e. in-spin aileron, causes what's called an accelerated spin. The nose drops, vertical velocity increases and rotation rate really accelerates. At least in the Pitts you feel as though you're tipping over into and falling down a hole that opened up in the sky! Recovery is easy unless you get disoriented, which can lead to incorrect control inputs. Mueller and Beggs noted that spin recovery is usually facilitated by a little in-spin aileron and retarded by out-spin aileron. I agree. The effects of aileron inputs on spin behavior is really fascinating. Try these out and let us know how the RV behaves. Bill

Cool!

Sounds fun..But I do run a 2.25" prop extension with a hartzell C/S prop so i am (very) relutant to add a whole bunch of power thru the prop in a spin due to the large Gyroscopic forces involved.

What I can tell you though the outspin aileron definately speeds up the rotation (goes a bit more nose down too). My video I posted shows with outspin aileron...Actually with no aileron the thing really hardly winds up at all.

Still can't get the thing to stall properly inverted to do inverted spins...I'm going to measure the down elevator to see if i can bet more down to give a good stall break when inverted.

Frank

No RV spin experience here

Carl,
Thanks for the invite to your thread and the kind words regarding my flight experience.

I've got to complement you on putting out some really nice videos.

My multitude of spins are all in the mighty T-34C TurboMentor... an aircraft rung out by test pilots right after I was born... so there isn't much envelope left for me to explore, and plenty of procedures and regulations that were written after folks killled themselves....

Any ways your initial spins seemed to have an accelerated stall type of entry... which as others here have commented isn't the 'typical' or preferred method (according to T-34C procedures) of entering a spin...

We climb to 9500' agl and set 30 degrees nose up attitude, reduce power to 200ftlbs of torque (turbo prop lingo) which is our simulated feather power setting (no low prop pitch drag, but no thrust either) and wait for stall warning indications. We then reduce power to idle feed in rudder and bring the stick straight back. The idea is to hit the stops as the plane stalls and is very nose high. Its really a gentle entry and the plane flips over on its back as it yaws and rolls in the entry direction...

We hold the rudder full in and stick straight back until the spin stabilizes... this takes about 2 turns, but we always check airspeed to be stabile between 80-100 kias... once stabile you are in a steady state spin (a bit slower roll rate I think than you are getting in your RV due to the strakes mounted on the empanage to dampen our roll rate in a spin).

If you put any other inputs in (especially aileron into the spin direction with a tad bit of elevator off the stop) prior to reaching a stabilized spin the plane likes to enter a spiral... I've been told this is due to unstalling the outboard wing while the inboard stays stalled.

If you are not in a steady state spin the T-34 will quickly recover when the controls are neutralized (rudder, elevator, aileron).

We commonly climb up to 13,500 AGL enter a stabilized spin like described above, release the controls and watch them float, the aircraft does not recover... this is called a control realease spin. Then apply opposite rudder with the stick straight back at the stops the roll rate slows then stops then SNAPS VIOLENTLY into the RUDDER, the nose pitches way down, airspeed screams up then the nose rizes, the roll rate slows and the airspeed stabilizes between 80 to 100 kias again... this is called a progressive spin

Opposite rudder and stick slightly forward of neutral typically recovers from the stabilized spin in under two turns. If in and inverted spin (typically you'll need to stall inverted to iniate one) you do not need the forward stick to initiate recovery. Intentional inverted spins are prohibited in the T-34 as they are very disorienting (you have to use the turn needle not your eyes to deterimine the direction of a spin because of this).

Test pilots have reported Neutral Idle frequently will recover a spin if left in for sufficient time, but opposite rudder stick slightly forward of neutral does it quicker and more reliably.

We have to use the slightly forward of neutral stick due to the horizontal stabilizer blocking the air flow over the rudder. We are also trained to push the stick full forward and hold it there if opposite rudder and stick forward of neutral do not initiate a normal recovery. If the full forward doesn't work keep it full forward and use maxpower as well to recover as aft CG's produce flatter spins and they may require the thrust of the prop to blow suffiecient air over the rudder to make it effective in breaking the yaw. Break the yaw, you break the stall... and then you start to fly again.

The key with the T-34 is to keep neutral aileron through the entire thing or you may leave a spin and enter a spiral.

Hope this helps.

Tom


PS Student Naval Aviators do their first spin typically on their 7th or 8th VFR flight in the T-34 (they will have done about 10 other insturment only flights by then too)... for me it was my 7th VFR flight ever (17th flight counting 7 sim rides and three hops under the hood instrument only)... so we make spining a very mechanical route memory process... introducing it early to students and not the fun you seem to be having wringing out your RV!

spins

The late Bob Herendeen used to do 30 turn plus inverted flat spins in his Pitts S1S. I timed him twice doing about 32 turns in 58 seconds. This is just under 200 degrees per second. The only spin that approaches 400 degrees per second is the accelerated spin. For training purposes this is normally started from a standard 1 G entry. After the autorotation is established the stick is moved well forward of neutral elevator(upright spin). The rate of rotation increases very rapidly. In the Pitts with idle power, the airspeed slowly increases. The pitch attitude is quite vertical. If power is increased the airspeed will continue to increase. Recovery is very quick and positive using opposite rudder and ailerons neutral. Depending on the amount of forward stick the elevator should be quickly neutralized during recovery. Aileron is NOT a key control in the accelerated spin. The spin accelerates to an alarming rotation rate with neutral aileron.
Flat Spins: In the Pitts and most Lycoming powered aerobatic aircraft the flat spin is left rudder upright and right rudder inverted. Normal upright spin entry, power idle,left rudder, after the autoratation is established the stick is moved all the way to the right. The left wing will come up, the nose will come up and the rotation will slow slightly. Now smoothly adding full power the left wing will come up some more, the nose will come way up and the rate of rotation will increase. Moving the stick forward will cause a modest increase in rotation rate, but not nearly as rapid as the previous spin. The key input in the flat spin is full power(gyroscopics).There are two primary recovery methods in the Pitts. 1. power to idle, simultaneous full right rudder, stick in forward left corner. 2. power to idle, full right rudder, release stick. A third method is to simultaneously apply right rudder and stick in left forward corner, full power throughout. The Pitts will consistently recover in 1/8 turnusing full power. The full power recovery should be approached VERY carefully, and is not suited to aircraft that are not unrestricted aerobatic aircraft(Pitts, Extra etc.) The Meuller/Beggs hands off recovery works in most popular aerobatic aircraft. It does not work in the Cessna 150 or AT6. There have been some posts indicating that it does not work in at least some RV's.
My comments are motivated by my perception that RV pilots are trying things such as outspin aileron without understanding all the ramifications. There has been a non fatal accident in England(not RV) where the initial actions in a long chain of events were an intentional spin with outspin aileron to "enhance the spin entry". The spin went bad, the engine quit, and after recovering the airplane was damaged in the off airport landing.
Pilots who have recieved formal spin/aerobatic training rarely have problems. Teaching yourself is like playing Russian Roulette.

further info

Hi,

Thanks for the posts - always interesting to learn more background from the edges of the flight training envelope practitioners. My background and training is limited to "basic" aeros, but reading about some of the 'other' aeras is very interesting. For me the RV isn't really a 'serious aeros' platform, if I want to go and learn & develop inverted / advance spinning - I'll find someone with an 300L / S2A

The differientiation between spirl dive vs stabilised spin is something that I haven't realised / had clarified before. I remember doing 'spiral dive' recognition during basic training, cut power, wings level etc.... but didn't understand that a stabilised spin / spiral dive could appear initially to be quite so 'similar'. My take away is cut the power and then get the ailerons netural is imediate action, then worry about rudder / elevator. Any other comments?

Second question, for my background education - it appears any 'normal' aircraft problems with spin recovery tends to come from aft CofG / air flow masking of the rudder - are there any generic approaches for the memory bank for if the normal recoveries don't work - is it mainly keep the opposite rudder to turn full in and pump the elevator stop to stop? Or is it a 'all depends' on the aircraft etc - any generics for RVs?

Thanks for your time,

Carl (still filling / sanding preping for paint! )

The google earth thing is awesome, it really is amazing what's around if you know the right buttons to push,cheers Mat

Google earth spins

mcwreford said:

The google earth thing is awesome, it really is amazing what's around if you know the right buttons to push,cheers Mat

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Thanks for the complement - no-one else has commented, but I almost like more than the video!

http://www.rvproject.gen.nz/kml/ZK-VII_2turn_spin.kmz

("Just a case hitting all of the buttons but not necessarily in the right order! - thank you Mr Preview" )

Carl