Spin testing observations - feedback requested

[zkvii]

Originally Posted by Bill Dicus

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

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

[asav8tor]

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.

[zkvii]

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

[Bill Dicus]

Good going. Bill

[frankh]

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!..

[Bill Dicus]

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

[frankh]

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

[Top_prop]

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!

[jrs14855]

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.

[zkvii]

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! )