Power-On vs Power-Off Stall Speed

[XBe02Drvr]

The 38' had a fatal accident rate that was, as I recall, six times that of the C-150 series; that's using the FAA's per 100,000 hours flown statistical model.

I wonder if those were a valid comparison. Large numbers of Cessna 150s escaped the flight training regime entirely, while I don't recall there being many privately owned PA38s. We had a number of 150 owners around the field who could have afforded bigger planes but chose their bird for its low operating cost, as they'd rather go flying every evening than spend the week working overtime to afford to take a Skyhawk, Skylane, Arrow, or Bonanza out on Saturday. Besides the 150 would comfortably drop into those little grass strip pancake breakfasts that the faster birds found kind of tight. These folks built time on their 150s near as fast as the flight school did.
Cheers,
Wes

 

[FSG43]

Recovery from a spin is power off, opposite rudder, nose down right?

You have the idea, but, as taught to many students:

1. Check direction of turn (yaw).
2. Throttle closed (power to idle).
3. Ailerons neutral (centered).
4. FULL opposite rudder (opposite direction of rotation).
5. Elevator positively and progressively forward to "break" the stall (unstall the wing).
6. When rotation ceases, neutralize (center) the rudder and ease out of the ensuing dive.

Most small GA SEL airplanes lose about 250 to 400 feet of altitude per one full turn of the spin. The incipient phase add about another 200 to 300-feet of altitude loss before the airplane is fully engaged in a sin.

As an FYI-- there are a number of reasons why the rudder movement occurs before the elevator movement. The affect of opposite rudder is to begin stopping the spin rotation and cause the nose of the airplane to pitch down. The blanketing of the rudder by the elevator is usually less, and as such, the effectiveness of the rudder is greater when the elevator is in the up position.

There are a number of SEL airplanes that should not be spun. The primary reason for this is because there are quite a few airplanes where the horizontal stabilizer/elevator combination acts as a shield to the airflow over the rudder making it ineffective to stop spin rotation. Rule of thumb: the more rudder surface area below the hor-stab-elev combo, the better spin rotation stoppage opportunity. Then as with some airplanes, there's an airflow disconnect along the fuselage beginning in the vicinity of the wing root.

The failure of airplanes to have satisfactory spin recovery characteristics can usually be attributed to one or more of the following:

1. Shielded rudder (by the hor-stab-elev combo).
2. Ineffective fuselage section that produces a low dampening. This is why one sees various and sundry types of strakes on the rear fuselage sections. They tend to generate usable, anti-spin, vortices.
3. Heavy wing-- fuel storage locations (tip tanks, outboard wing fuel tanks), wing lockers, engines on the wing. These all help to increase the tendency to predominate the moment of inertia. It's sort of like twirling a broomstick without end weights versus one with weights firmly affixed to its ends. Which would be easier to stop twirling? Airplanes with the mass spread out along the fuselage usually recover from spins than one where the weight is spread along the wing.
4. Weak wing structure resulting in a changing airfoil shape (giving an unknown aerodynamic performance) and airflow patterns.
5. In sufficient arm for rudder to be effective; especially with a longer nosed airplane (weight location again).

Look up the old NACA film on how they took a very bad spinning airplane, Grumman AA-1, and created one which would spin nicely, albeit fast, but one whose spin which normally could not be recovered from (without a spin chute) to one where the spin could be recovered from. Probably on YouTube somewhere.

Spins are fun and all pilots should be well-versed in the knowledge of them as well as performing at least a two-turn spin. Word of caution: As I recall, the FAA certification only requires a three-turn spin capability and recovery for Utility category airplanes (usually used for training). Anything beyond that the pilot becomes the test pilot. In my younger years I foolishly did ten-turn spins in C-150's and 172's after a long day of instructing. Rotation was fast and recovery required between two and three rotations due to the small rudder area. I too was fortunate to have not drilled into the ground.

Enjoy your evening guys,

F

 

[FSG43]

I wonder if those were a valid comparison. Large numbers of Cessna 150s escaped the flight training regime entirely, while I don't recall there being many privately owned PA38s. We had a number of 150 owners around the field who could have afforded bigger planes but chose their bird for its low operating cost, as they'd rather go flying every evening than spend the week working overtime to afford to take a Skyhawk, Skylane, Arrow, or Bonanza out on Saturday. Besides the 150 would comfortably drop into those little grass strip pancake breakfasts that the faster birds found kind of tight. These folks built time on their 150s near as fast as the flight school did.
Cheers,
Wes

Those were reliable numbers Wes.

 

[FSG43]

Those were reliable numbers Wes.

The fleet sizes were statistically weighted.

 

[XBe02Drvr]

The fleet sizes were statistically weighted.

Got it. Thanks!

 

[XBe02Drvr]

they took a very bad spinning airplane, Grumman AA-1, and created one which would spin nicely

Was that the AA-1, or its predecessor, the BD-1? Was that spin the reason they would never give "Bigmouth Jim" a type certificate for his everyman's airplane? I remember reading exciting articles about how everyone would have one in their garage. At the time I thought it a bureaucratic travesty, but eventually came to realize why the powers that be would consider a "volksflugzug" a scary thought.
Eventually got to fly a Yankee and realized how underpowered it felt with an O-235; can't imagine it with an A65.
Cheers,
Wes

 

[FSG43]

Was that the AA-1, or its predecessor, the BD-1? Was that spin the reason they would never give "Bigmouth Jim" a type certificate for his everyman's airplane? I remember reading exciting articles about how everyone would have one in their garage. At the time I thought it a bureaucratic travesty, but eventually came to realize why the powers that be would consider a "volksflugzug" a scary thought.
Eventually got to fly a Yankee and realized how underpowered it felt with an O-235; can't imagine it with an A65.
Cheers,
Wes

No idea about the BD-1. BMJ was an innovator and promoter from my recall. Just know about the NACA spin related work on the Yankee. Like many good ideas, that poor little bird had some unintended negatives. I never had the opportunity to fly the 2- seaters, only the 4-seat versions. My recall is they were cramped for tall guys like me, powered adequately and were neutrally stable making them mediocre trainers and an airplane the "average" pilot had to pay close attention too.

I'll search around for that NACA film. Most interesting. Will pass on the link if I locate it.

Blue skies and light winds,

F.

 

[special ed]

After comments on this thread about the AA-1A, I read accounts on line about the flight characteristics. My late friend had one and we flew in it often. My flying after solo ended with marriage and kids. I had stick time with him at times and was impressed with the light stick pressures. Thumb and finger. But I now know why he was reluctant to land at a grass strip when we (a two plane flight with a c 172) out for a Saturday flight. I now have a better appreciation of his skills as he weighed about 240 pounds and I was just under 200. He was a CFI and often gave me the stick and another time he wanted me to land at an uncontrolled airport with no traffic. As we began final, although the aircraft was steady, I could get a feeling that it wanted to pitch up, no stall warning sound and plenty of speed , but it didn't feel right, so I gave it back. One of our group had a Tomahawk, and after this thread I called him and asked if we should get tee shirts made saying we survived Tomahawks and AA-1A.

 

[MIflyer]

With a Cessna 150/152 spin recovery first you release the back pressure. Actually shoving the nose down is not recommended, although that is what I did the one time I entered a spin semi-accidentally. Then you apply opposite rudder and roll to the opposite direction, which usually is going to be to the Right, especially if you have any power in. You do not roll before you release back pressure and break the stall because the ailerons will make the stalled condition worse on the wing you are trying to raise. Some people even say you do not use the ailerons at all until you have used the rudder to get the airplane rolling in the opposite direction. Some airplanes do not have washout on the outer wings or differential ailerons and using the ailerons will make things worse.

Several years back locally we lost a pilot and her brother when they went out in Cessna 152 and stalled/spun, apparently while circling a lake in a remote area. Doing steep turns while looking at something on the ground is one of the best ways to have a stall/spin creep up on you.

The A-7D has a problem that it can stall and then enter a "post stall gyration." If it is in a post stall gyration rather than a spin and the pilot applies standard spin recovery techniques it will never come out of the spin. There was a proposal to install a device that would automatically detect a post stall gyration and activate a flap to recover, but I do not think this was ever installed on USAF aircraft. I heard about the A-7D problem because it was proposed that a modification of that same box would enable us to replace an F-106A component that had been in service so long we no longer had any spare parts or adequate technical data for it. So I got the prototype A-7D box and was going around SM-ALC getting into F-106A nose gear wheel wells to see if it would fit.

 

[fliger747]

As an example of the unreliability of memories from 50 years ago, I can't recall how much altitude is lost in a Cessna 150 with a prompt spin recovery, but maybe 500 ft? At low altitude the promptness of the response might make the difference between UCFIT and not. A good argument for training! It was a fun maneuver, the plane would at the break with rudder flip right over the top and was very low G except for the pullout since the plane was pointing directly at the ground.

Taking my commercial check ride I was demonstrating a dirty stall in a Piper Arrow. I noticed the examiner scanning the area below. At the break he booted full rudder and over the top into a spin! Recovery was prompt with a similar technique except for whatever reasons I retracted the flaps.

Post stall gyrations are a phenomenon associated with "roll coupling" and is mostly found in aircraft with a concentration of mass along the length of the fuselage. The simple explanation is that once spinning, insufficient aerodynamic force exists to counter the inertia.

Cheers: T

 

[FSG43]

With a Cessna 150/152 spin recovery first you release the back pressure. Actually shoving the nose down is not recommended, although that is what I did the one time I entered a spin semi-accidentally. Then you apply opposite rudder and roll to the opposite direction, which usually is going to be to the Right, especially if you have any power in. You do not roll before you release back pressure and break the stall because the ailerons will make the stalled condition worse on the wing you are trying to raise. Some people even say you do not use the ailerons at all until you have used the rudder to get the airplane rolling in the opposite direction. Some airplanes do not have washout on the outer wings or differential ailerons and using the ailerons will make things worse.

Several years back locally we lost a pilot and her brother when they went out in Cessna 152 and stalled/spun, apparently while circling a lake in a remote area. Doing steep turns while looking at something on the ground is one of the best ways to have a stall/spin creep up on you.

The A-7D has a problem that it can stall and then enter a "post stall gyration." If it is in a post stall gyration rather than a spin and the pilot applies standard spin recovery techniques it will never come out of the spin. There was a proposal to install a device that would automatically detect a post stall gyration and activate a flap to recover, but I do not think this was ever installed on USAF aircraft. I heard about the A-7D problem because it was proposed that a modification of that same box would enable us to replace an F-106A component that had been in service so long we no longer had any spare parts or adequate technical data for it. So I got the prototype A-7D box and was going around SM-ALC getting into F-106A nose gear wheel wells to see if it would fit.

Here is a pretty good article on the "Yankee" series airplanes: Aviation Consumer - The AGAC AA-1

About spin recovery in the C-150/152 series-- The C-150/152 series POH advises, "1. Retard throttle to idle position." followed by, "2. Apply full rudder opposite to direction of rotation." Then, "3. After 1/4-turn, mokve control wheel forward of neutral in a brisk motion.." I've had some students take this to the extreme, luckily we were slow. And, "4. As rotation stops, neutralize rudder, and make smooth recovery from the resulting dive." Usually can be done with sufficient altitude. Elevator before rudder can create an unwanted situation as I mentioned earlier.

I'm not certain what you mean when you said, "You do not roll before you release back pressure and break the stall because the ailerons will make the stalled condition worse on the wing you are trying to raise. Some people even say you do not use the ailerons at all until you have used the rudder to get the airplane rolling in the opposite direction. Some airplanes do not have washout on the outer wings or differential ailerons and using the ailerons will make things worse."

If you're talking about spins, a deliberately performed spin is performed with ailerons neutral.

If you're suggesting that coordinated controls not be used during stall recovery (getting wings level from an unannounced roll) you are correct IF you're piloting an airplane that was certified before 1946. It was back then that the CAA realized there had to be better ways to improve control during the stall. The new rule lead to slots in front of the ailerons and eventually to wing washout and differential ailerons. EVEN WITH differential ailerons, misuse can lead to an adverse yaw induced roll and even spin if the aileron input is held in position and the wing is fully stalled.

There are many CFI's who were taught by the "old school guys" who learned and taught rudder only for roll authority during stalls. That CAN, as I found out years ago, and subsequently demonstrated to my students (PVT thru CFI), get the unwary pilot into deep pooh-pooh. Aileron only use can also lead the pilot into a place he/she doesn't want to enter; especially if they keep the airplane stalled.

Many of these old school guys were good, don't get me wrong. However, what THEY learned often did not get updated. As such, they passed on a mediocre procedure to stall recovery. Seen this repeatedly. Some refused to use landing flaps because, "...those are only for emergencies and short runways... ." I'm not kidding.

When you stated, " Some airplanes do not have washout on the outer wings or differential ailerons and using the ailerons will make things worse." you were partially correct. Bottom line-- know your mount before taking it skyward. Period. Know about its certification standards/date, rudder above or below the elevator, airframe loading (dumb-bell type wing, fuselage or...?), airfoil characteristics, etc., etc., etc. A Piper J-3 isn't one where you'd use coordinated controls during stall recovery to maintain wings level configuration for the very reason you expressed. But, Not the "modern day" airplanes.

Many LSA airplanes from foreign countries do not have wing washout, differential ailerons, etc. Want to read a tragic accident report where a sweet bird was mis-used as a primary trainer ultimately killing off two wonderful people? Dig up the 01/23/2010, Waxahachie, TX, accident involving the beautiful Tecnam P-2002. Look at the various pics of a whole 2002 and read about it... .

When the industry is forced to go "cheap" for whatever reason(s) one wishes to ascribe, we end up with problems. The EAA, AOPA and FAA did not do GA any favors when they created the LSA rule. It prevented one of the best trainers ever made from being used due to the idiotic weight limit imposed by the LSA rule. Trainer? The Cessna 150/152 series airplanes.

Must trundle off to the doc's office, stay well and keep smiling,

F.

 

[XBe02Drvr]

The A-7D has a problem that it can stall and then enter a "post stall gyration." If it is in a post stall gyration rather than a spin and the pilot applies standard spin recovery techniques it will never come out of the spin.

Not just the A7. The F4 ACM training squadron I used to work with had fairly frequent "departures from controlled flight" as over-eager nugget aviators tried to bend the laws of physics to get a Sidewinder tone on those pesky A4s. The F4 had an anything but straight forward post stall gyration, and a misdiagnosis and inappropriate recovery technique tended to lead to a unrecoverable flat spin and a Martin-Baker landing. The gyration was characterized in NATOPS as "irregular oscillations about all three axis accompanied by random gross fluctuations of rate of turn, coordination, airspeed, and AOA indicators". The instructor RIOs were all expert spin recovery coaches, and were granted "silver tongue award" patches for their "dirty shirt" flight suit for each save.
Our film library had training films on F4 spin characteristics with flight test footage from cockpit, instrument panel, and chase plane perspectives that were downright mind bending. Not your average 150 Acrobat.
Cheers,
Wes

 

[XBe02Drvr]

It prevented one of the best trainers ever made from being used due to the idiotic weight limit imposed by the LSA rule. Trainer? The Cessna 150/152 series airplanes.

My sentiments exactly!!

 

[FSG43]

My sentiments exactly!!

It's too bad the GA community is unable to get the FAA to revise the LSA rule to include SEL's with 2-seats weighing up to 1,650-pounds MGW. Might be a chance to open up LSA training with reliable and safe training airplanes that put the composite selection to shame. Oh well... if wishes were horses, beggars would ride.

Many years ago I was quite insensed by the LSA weight limit. Nobody at the EAA or AOPA would/could tell me WTH was up with what appeared to be an arbitrary GW weight limitation. After calling a number of buddies in the FAA-DC HQ, I was directed to a fellow who was supposed to have been part of the LSA project /working group that developed the rules. When asked about the weight limitation reasoning and why GREAT training airplanes like the C-140/150/152 weren't allowed he hemmed and hawed a bit. Then, after the umpteenth "umm," he told me: 'Well, we figured the mass inertia of a Cessna hitting the roof of a home versus an LSA weighing 1,320-pound hitting it. We concluded there would be less damage to the house with the lighter airplane.' A jaw-dropping and mind-scrambling answer. Attempted to discuss the sense of what he stated and got nowhere. No idea how factual what he said was.. but he did say it. Maybe he knew it would light my fires, maybe not. But he sure was seriously dead pan abput the whole issue.

The LSA concept was a good idea that was poorly executed. It could have been a gateway to increasing the pilot population, something our wonderful Nation needs. The way it is now, with expensive airplanes, more than a few possessing questionable aerodynamics/design and structures, and incapable of carrying the 'larger' American "2-crew" it's another good-idea diluted into uselessness and placed into a corner where it's minimally used. Sad outcome for the "new industry" so many had hoped for.

 

[Icorps1970]

I thought spin recovery was part of pilot training? Especially with propellers and torque & p-factor.

Its considered an acrobatic maneuver by the FAA. When I was teaching people in Cessna 150, 152, 172 they ALL knew spin recovery. Though the 172 generally needed a shot of power and rudder to start otherwise would just rumble. CFI required a 3 turn spin and recovery in the log book, but its not legal in anything but an aerobatic a/c IIRC. The FFA check ride guys were not interested in actually doing it in my experience. I had a solo student who developed bad habit of dynamiting the left rudder when the A/C stalled. He did this twice on one dual flight so I had him take me up to 5000, this was sea level ANC, AK and had him do me a power on stall. The 150 rolled over on its back then started a normal spin. He broke the spin before it made one turn since we had done them before, but now we were headed straight down and he was screaming. I pulled the power and told him if he did not pull out we would hit the trees (the Spuce trees looked perfectly round out the wind screen). He did a nice pull out with me making sure he did and Wilmer (yeah) never did this again. I again told him what the mistake was and that stalls were not dangerous or even scary when done right. However, from my experience with 3365J when I was a young primary pilot building my solo time, one could scare one's self in a C-150. So I taught spin recovery to everyone. Probably did with the Cherokees too but don't remember much less time in them.

 

[Icorps1970]

Curriculum = Practical Test Standards is the proper term but now known as "Airman Certification Standards." Removed sometime in the 1970s IIRC

I started flight school in 1971 when I got out of the Army and spins were not taught then. Don't know when it was dropped. When I was flying it was illegal to do them in an a/c not certified for acrobatics. But CFI candidates had to do a 3 turn spin and recover and have it in the log so...

 

[XBe02Drvr]

But CFI candidates had to do a 3 turn spin and recover and have it in the log so...

Back then there was a "carve out" in the FARs that allowed certain "acrobatic" maneuvers (chandelles, lazy 8s, steep 720s, spins: your classic "commercial maneuvers") to be done in Utility Category Aircraft, IF they were MANUFACTURER APPROVED for THAT AIRCAFT and were REQUIRED for a LICENSE or RATING and were conducted ONLY WHILE FLIGHT TRAINING.
Mandatory spins for Private Pilot were gone long before my time.I got my Private in 1970, Commercial in 1973, CFI in 1975, and haven't flown at all in this century, but those were the rules back then.
Cheers,
Wes

 

[Barrett]

Maybe we need to define our terms ref. Slipstream. But I've seen the effects of wingtip vortices up close. At the Abbotsford, BC, airshows in the late 60s into early 70s the duty Vulcan did pylon turns at REAL low level with that cavernous doomsday bomb bay gaping. Vortices swirled through the dirt/sand in visible swirls, accompanied by an eerie wail.

In 1969 the organizers wanted our antique aircraft group to trail the prototype 747 to show aviation progress or something. Made absolutely no sense for the older aeroplanes to trail the newest, apart from the safety concerns that shoulda been obvious. My dad was leader of the gaggle and said Hell No. So the committee found a young American who was eager to show off his new Mini Mustang, and agreed to the absurd schedule. Less than a minute separation.

POW! He flipped over and crashed inverted RIGHT THERE directly in front of me probably less than 100 yds. Brief flash of flame, then nothing. Killed on impact.

That remains my never-to-be-forgotten lesson in slipstreams, etc.

 

[fliger747]

Yes, I remember the Vulcan doing the turns around the infield at Abbotsford! very impressive!

Even flying the 747 one could get a decent jolt from the wake turbulence of another one!

 

[special ed]

I got to see the Vulcan do the low altitude routine at Barksdale AFB many years ago. A most unbelievable performance.