Spins prohibited

[bd32322]

Just curious about the aerodynamic reason for why its harder to recover from a Mooney spin than a Cessna 152 for example. I am not questioning Mooney's judgment on prohibiting spins in the mooney, just interested in the aerodynamics.

It stalls the same as any other plane and recovers mostly the same way .. so why can it not recover from a 1 wing stall easily .. aka spin

Thanks

[triple8s]

http://www.mooneyevents.com/spins2.html

[gregwatts]

I had a student that I was teaching in her own 201 Turbo Bullet. While trying to teach her slow flight and stall awareness, she pulled back on the yoke and within a second we were in a spin. We lost over 2000' before recovery.........two turns before I could break the stall.

 

It was a very abrupt and harsh stall! I absolutely don NOT encourage anybody to try a spin unless you are above 5000' and even then.........don't recommend it.

[M016576]

Just curious about the aerodynamic reason for why its harder to recover from a Mooney spin than a Cessna 152 for example. I am not questioning Mooney's judgment on prohibiting spins in the mooney, just interested in the aerodynamics.

It stalls the same as any other plane and recovers mostly the same way .. so why can it not recover from a 1 wing stall easily .. aka spin

Thanks

Probably because the rudder gets blanked a little bit in the spin.... That's just a guess, btw

[FloridaMan]

Mooneys are also supposedly capable of entering a flat spin. 

[Riq]

I had a wicked departure stall that resulted in a spin that the checkride instructor was amazed we got into.

 

It was seemingly only to the left, and we couldnt replicate it easily.

 

It sure got my attention because it flips a wing and goes down fast, but was easily recoverable.

[bd32322]

Hmmm I was not aware of this behavior in stalls at all. I just knew that recovering from spins was bad, not that it would be so easy to enter a spin. I have had my mooney for 2 years now and did practise full power off stalls. Didnt know I was on the edge of a spin.

I dont see where the sudden spin is coming from, unless there was some rudder input or the aircraft was not co-ordinated (prolly not the case in power off stalls).

Or maybe there was an attempt to correct a wing drop with aileron, which resulted in rudder input. I think the ailerons and rudder are somewhat linked because it seems to need very little rudder in turns.

[M016576]

Yep- it's called an Aileron Rudder Interconnect... I think it's just a bungee or a spring connecting the two in a mooney.

[Marauder]

Bill Wheat explained to me once that our Mooney's stall characteristics were very unpredictable prior to the addition of the stall strips that adorn our wings. Loss of aileron function due to outer wing stalls had a much higher probability of occuring -- leading to a spin. Adding the stall strips increased the stall buffet and more importantly allowed the wing root area to stall before the outer wing. This helps the stall characteristics but still does not eliminate spins from uncoordinated stall entry. I have noticed that it doesn't take much uncoordination in a stall to induce a wing low situation.

[Hank]

Bob Kromer wrote an article about spinning Mooneys during certification. I'll have to look for the link since I can't attach a Word file. He included recovery instructions, and said to make a 1-turn spin and recover took at least 2000'. He never entered below 6000' agl.

[PTK]

Just curious about the aerodynamic reason for why its harder to recover from a Mooney spin than a Cessna 152 for example. I am not questioning Mooney's judgment on prohibiting spins in the mooney, just interested in the aerodynamics.

It stalls the same as any other plane and recovers mostly the same way .. so why can it not recover from a 1 wing stall easily .. aka spin

Thanks

It has to do with our Mooneys' laminar airfoil wing. It is faster as there is less parasitic drag (surface friction) but the cost is that, as we approach the stall, the separation point of the airflow moves quickly forward. This is because the point of maximum camber in a laminar wing is further aft than on a conventional wing. They stall differently. The stall strips were added to give us an earlier warning of approaching stall.That section of the wing behind the stall strips stalls first, instead of the entire wing at once with no warning.

[tomn]

Can you guys give us more information on the springs mentioned. I was not aware of them. Where are they installed, do all models have them, etc.

Thanks, Tom

[tomn]

Thanks Jim, I'll look for them.

[kmyfm20s]

When I transitioned to a Mooney stall recovery was practiced a lot. I was fortunate to have a high time Mooney instructor that has been an instructor at some of the MAPA clinics. The difference from previous stalls that really stuck out was that with the laminar flow wing of the Mooney you really need to get a lot air flow back over by pitching the nose below the horizon and not level as many of us learned in the Cessnas. If we pitch to level horizon and not below we would hit a secondary stall. By the End of my stall training he had me going from recovering from power off stalls sequentially, stall, recover, stall, recover. I believe some of the spins people are talking about are from not aggressively recovering from the stall.

I believe there is a MAPA event coming up in California for those that would want more training.

[kmyfm20s]

Just curious about the aerodynamic reason for why its harder to recover from a Mooney spin than a Cessna 152 for example. I am not questioning Mooney's judgment on prohibiting spins in the mooney, just interested in the aerodynamics.

It stalls the same as any other plane and recovers mostly the same way .. so why can it not recover from a 1 wing stall easily .. aka spin

Thanks

I guess I didn't directly answer the question but difference is the laminar flow wing vs the high lift wing. Read the between the 2 but as I wrote above my training and experience between the 2 was different.

With the laminar flow (Mooney) wing you are going to need more air flow (more air speed) than a high lift wing (Cessna) to prevent one wing from losing lift before the other and entering a spin.

[M016576]

Just to clean up some of the terminology...Stall recovery is a function of angle of attack, not airspeed. To break a stall you lower the wings Effective AOA to below its critical value. If you exceed this critical AOA during recovery, you'll enter a secondary stall, and have a higher chance of entering a spin (mostly because now your control inputs are probably not as stable as during the initial entry, when you were expecting it).

Two types of flow: laminar and turbulent. Laminar is faster, but breaks free from the wing faster and stalls faster. Turbulent is slower, but capable of higher AOA's as the flow remains attached to the wing easier. Really in our "laminar flow" wing, we have both turbulent and laminar flow going on, the chord is just optimized to keep the flow laminar for longer than the thicker C and P brand NACA chords. Vortex generators are a way to induce turbulent flow further up the wing chord for higher AOA capability.

The difference between where the boundary layer changes from laminar to turbulent on our wing vs a cessna's is probably about 2 inches. But we also probably have to reduce our AOA an extra 3 degrees, that plus some rudder blanking due to the low wing and tail structure are my guesses why it takes a little longer to get out of a fully developed spin in a mooney. 2000' isn't that bad... The jet I used to spin would lose 8000-10000' feet on average, sometimes longer....

[Alan Fox]

Don't do it EVER.....EVER.....EVER.......    Inadvertent spin doing power on stalls , 3 spins and 1000 feet to recover .......I almost quit flying after that flight.......Instructor saved my ass ,

[Piloto]

All FAA approved single engine planes must  be spin recoverable as indicated by FAR 23.221

 

 

Sec. 23.221 Spinning.

(a) Normal category airplanes. A single-engine, normal category airplane must be able to recover from a one-turn spin or a three-second spin, whichever takes longer, in not more than one additional turn after initiation of the first control action for recovery, or demonstrate compliance with the optional spin resistant requirements of this section.

 

More details at http://www.astech-engineering.com/systems/avionics/aircraft/faapart23b.html#Spinning

 

The spin test is performed with full aft CG (sand bags in baggage) and full fuel. The cabin door is rigged for quick separation and the pilots are required to wear a parachute. The Mooney complies with FAR 23.221, even when long range tanks are installed. The FAA use a spin matrix that requires  about 50 spins in different aircraft configurations (flaps up/down, power off/max, gear down/up and combinations) for left and right rotation. Just don't try it at low altitude. On FAR 23.221 there is no altitude limit loss. But from my experience you can easily loose 1,000feet when performed at 10,000 feet. Just keep the speed up.

 

José

[Piloto]

I personally don't see any added safety value on having a plane to demonstrate spin recovery as per 23.221. It is not required on twins and most spin accidents happens on the traffic pattern when turning base to final. Which there is not enough altitude for a successful recovery. What should be emphasized on the training is the stall possibilities during turns, specially at gross weights and gusty conditions. I myself keep the speed at 90kts or higher, lower the flaps on down wind before the turn and maintain 90 kts until stablished on short final. If my speed is too high on the flare or long floating I raise the flaps 5ft before touchdown to prevent bouncing. Last week I saw two Acclaims at Premier having the engines removed for inspection because of prop strike during bouncy landings. Don't let this happens to you.

 

José    

[aviatoreb]

I personally don't see any added safety value on having a plane to demonstrate spin recovery as per 23.221. It is not required on twins and most spin accidents happens on the traffic pattern when turning base to final. Which there is not enough altitude for a successful recovery. What should be emphasized on the training is the stall possibilities during turns, specially at gross weights and gusty conditions. I myself keep the speed at 90kts or higher, lower the flaps on down wind before the turn and maintain 90 kts until stablished on short final. If my speed is too high on the flare or long floating I raise the flaps 5ft before touchdown to prevent bouncing. Last week I saw two Acclaims at Premier having the engines removed for inspection because of prop strike during bouncy landings. Don't let this happens to you.

 

José    

 

Two?!!!  Ouch.

[jetdriven]

I personally don't see any added safety value on having a plane to demonstrate spin recovery as per 23.221. It is not required on twins and most spin accidents happens on the traffic pattern when turning base to final. Which there is not enough altitude for a successful recovery. What should be emphasized on the training is the stall possibilities during turns, specially at gross weights and gusty conditions. I myself keep the speed at 90kts or higher, lower the flaps on down wind before the turn and maintain 90 kts until stablished on short final. If my speed is too high on the flare or long floating I raise the flaps 5ft before touchdown to prevent bouncing. Last week I saw two Acclaims at Premier having the engines removed for inspection because of prop strike during bouncy landings. Don't let this happens to you.

 

José    

 

A lot of those prop strikes, probably most of them, are from coming in too fast to land. 90 knots in an M20J is 1.5 times V_SO, or 20 knots too fast.  The book recommends 1.3 V_SO. 

[M016576]

AOA control is critical. Whether it be via calculated airspeed or an Indexer....

Amazing how many of these beautiful, super expensive aircraft end up in the shop with terrible damage that's 100% preventable with a little more training / flight discipline.

Or perhaps the pilot doesn't even realize their error until its too late.... If only we all learned with and had stock AOA gauges... I bet both incidences of approach turn stalls and "fast landings" would drop off significantly....

[marks]

There's much correct info above, but in short the wings are big and long and don't quickly fall, while the rudder is small and since it leans forward, is easily blanked.

[RocketAviator]

AOA control is critical. Whether it be via calculated airspeed or an Indexer....

Amazing how many of these beautiful, super expensive aircraft end up in the shop with terrible damage that's 100% preventable with a little more training / flight discipline.

Or perhaps the pilot doesn't even realize their error until its too late.... If only we all learned with and had stock AOA gauges... I bet both incidences of approach turn stalls and "fast landings" would drop off significantly....

 

Agreed that is why I installed an AOA during the panel upgrade!  Great tool!  

Fly Safe,

Rocket On!

[201er]

Agreed. Guys, I keep coming back to this. Get an AOA indicator! After seeing it creep critically low in some heavyweight or steep turns (with what would appear to be a fair bit of airspeed), I have learned a ton about stall prevention in my aircraft. It has also saved me when climbing out at extensively varying weight conditions from 250-980lbs of payload. Watching the airspeed indicator alone won't save you from stalling cause you don't always know what speed at that weight, flap, or turn condition will cause you to exceed the critical angle of attack. The AOA doesn't care and tells you what your margin from stalling is at whatever condition you are in at the moment. In retrospect my flight instructors did a thoroughly inadequate job preparing me to realize the many other ways to induce a stall because we pretty much only focused on straight power on/off stalls in the same weight configuration!