Power-On vs Power-Off Stall Speed

MIflyer · Jun 4, 2019

The first "private jet" was a T-33A assembled by a guy who bought all the pieces as surplus and built one. He had an idea that with the new DC-8's and 707's the airlines would pay well for a jet they could use for training, But even after he got the airplane completed he could not get it licensed. Lockheed had never built it; it had no serial number. But then the USAF sold a surplus wrecked T-33A and sold it as an airplane rather than a pile of aluminum; he bought it and appropriated the serial number, which he used to get an airworthiness certificate and an N-number.

Another guy built up a T-38 out of surplus parts in the late 80's. It appeared in some commercials.

XBe02Drvr · Jun 4, 2019

MIflyer said:
Added to that was the Kinner radial engine

The "Kinner Killer", according to WWII aviators whose stories I've heard. Apparently they were prone to quitting dead on occaison when throttled back in flight. That, coupled with an airframe whose landing behavior was not well adapted to dead stick off airport landings, led to many unnecessary fatalities.

gumbyk · Jun 4, 2019

XBe02Drvr said:
The "Kinner Killer", according to WWII aviators whose stories I've heard. Apparently they were prone to quitting dead on occaison when throttled back in flight. That, coupled with an airframe whose landing behavior was not well adapted to dead stick off airport landings, led to many unnecessary fatalities.

Never had any problems with the handling of the PT-22, and it was my first tailwheel aircraft. In fact, I'd think that the long-travel undercarriage would help with off-airport landings; it was the one thing that took the most to get used to. You'd feel the wheels touch, but you were still almost a foot from having significant weight on the wheels. I think if you tried to 'drive it on' from this point you'd have problems. Three-pointing it on was preferable for me.
The stall was 'positive' but nothing scary, spin recovery wasn't anything overly dramatic, unless you got carried away with checking forward.
I'd love to fly one again.

XBe02Drvr · Jun 5, 2019

gumbyk said:
Never had any problems with the handling of the PT-22, and it was my first tailwheel aircraft.

Lucky dog! After the stories, I'd heard, I was curious to see one up close and personal, and maybe get to fly it. In a lifetime of knocking about airshows and museums, I've never actually seen one in the flesh. Seen all the other PTs, BTs, and ATs (except the AT9), and been up in the Stearman, the PT26, and the Chipmunk, but never crossed paths with the Ryan.
The Chipmunk was an experience. It had been re-engined with a pepped up Ranger that turned opposite direction from the original British engine, making the vertical stab offset and the wing wash work the wrong way. You had to fly around with your foot heavy on the rudder to keep it straight.
Cheers,
Wes

special ed · Jun 5, 2019

The recent golf course landing by Harrison Ford was in his PT-22

MIflyer · Jun 5, 2019

Yes, Ford's PT-22 had its carburetor fall apart. And apparently those airplanes have a power off sink rate somewhere between that of a Baldwin Piano and a Baldwin Locomotive.

XBe02Drvr · Jun 5, 2019

MIflyer said:
those airplanes have a power off sink rate somewhere between that of a Baldwin Piano and a Baldwin Locomotive.

Ideal for off-airport dead stick landings by student pilots, no?

MIflyer · Jun 5, 2019

Some years back I climbed in my friend's Waco and we few over to Zellwood for a small fly in. Both a PT-22 and a Ryan ST showed up and parked side by side. It was interesting looking at the differences. Somewhere I have pictures. The PT-22 was definitely a "value engineered" version. I understand that the swept back wings made the PT-22 easier to stall/spin if you got too slow, say on a turn to final. I wonder if that aerodynamic "refinement" was to produce a "better" trainer or just the result of a CG change from switching to the radial engine,

A guy in NC built a Ryan ST from scratch a while back. I've often thought it would be fun to convert a PT-22 to an ST with new wings and a Walther in-line engine.

XBe02Drvr · Jun 5, 2019

MIflyer said:
I've often thought it would be fun to convert a PT-22 to an ST with new wings and a Walther in-line engine.

All the Empi hotrod parts in the world can't make a 40 horse VW beetle into a Porsche 356. Silk purses are silk purses, and sow's ears are sow's ears, and never the twain shall meet. (Sorry, Rudyard!)

Ivan1GFP · Jun 5, 2019

Zipper730 said:
I have a few as well: Ironically, this was before a diagnosis of Asperger syndrome, I was watching a movie (Rain Man) -- it was in class, I don't really even remember why we were watching it, but go figure. I just remember the character annoying the hell out of me, and I couldn't figure out why, and I remember being told that people often dislike traits they have in others. Usually the undesirable or annoying ones.

It did raise a question, I was an odd-ball, and had been misdiagnosed half a million times in all sorts of ways, and I remember wondering if I had some kind of "autism light" (I didn't know Asperger syndrome was a diagnosis until 2000), and I was told that most people with that are unable to speak and stuff.

So I dropped the idea. A therapist I saw later had considered the possibility I could have it, though I wasn't formally diagnosed. That came in 2001-2002 (I was 18).

Hello Zipper730,
I have had years of experience dealing with the Special Education programs in the modern school systems.
My Wife is pretty convinced that *I* am also an Aspergers. I can definitely recognize many of the characteristics.
There is often a very fine line between Aspergers, Autism, Attention Deficit Disorder and other issues and I am not convinced that a single diagnosis is really a complete picture. I see it more as a classification at a particular time and from the standards of observation that have been related to me, it is very often a judgment call on the part of the observer.
These observers vary quite a lot in quality. They usually have multiple charges and come into a classroom for just a few minutes for an observation. The positive or negative observation is made in a vacuum generally without context of what else may be happening in the classroom, so one has to wonder about validity. Observations tend to be infrequent, so unless there is nearly constant abnormal behaviour, it may not be noticed except by chance.

FWIW, Aspergers Syndrome is no longer a distinct diagnosis in our school system. (All those former Aspies are cured?)
Aspergers is now considered "Autism Spectrum". As you know, looking for characteristics specific to Autism will probably not work well for most Aspergers people.

This should hit pretty close to home for many of us. I suspect that there are more than the average number of Aspergers kids among us.
I know that in the older IT industry, a very large proportion of my co-workers showed some Aspergers characteristics.

- Ivan.

XBe02Drvr · Jun 5, 2019

Ivan1GFP said:
I know that in the older IT industry, a very large proportion of my co-workers showed some Aspergers characteristics.

The former director of guidance at the school I used to work at has said privately she's convinced that any brilliant, dedicated, workaholic techie is by definition subject to Aspergers. Without it, she felt, they would not be effective and successful in their field.
Cheers,
Wes

Zipper730 · Jun 6, 2019

Ivan1GFP said:
My Wife is pretty convinced that *I* am also an Aspergers.

Possible, on a forum like this with an interest in aviation, it'd work pretty well as you'd be able to retain huge quantities of information on stuff. There are cases where my skills in math (not all that good) can be compensated for by simply using certain rules of thumb to guesstimate stuff. There are lots of patterns and rules that nature follows, so if you can tap into those, you can start making guesses that are decent.

That said, I learned more about piston engines on this forum than actually having a car.

There is often a very fine line between Aspergers, Autism, Attention Deficit Disorder and other issues and I am not convinced that a single diagnosis is really a complete picture.

I was diagnosed as having ADD as a kid -- I was a hyperactive maniac who liked to run around and have fun. I had trouble sitting still and stuff. Later on they misdiagnosed me with bipolar disorder, and later the Asperger Syndrome diagnosis came into the focus.

It's now classified as high functioning autism, but basically, the changes are that it's classified differently. That's partially why there are higher diagnosis rates.

gumbyk · Jun 6, 2019

MIflyer said:
Some years back I climbed in my friend's Waco and we few over to Zellwood for a small fly in. Both a PT-22 and a Ryan ST showed up and parked side by side. It was interesting looking at the differences. Somewhere I have pictures. The PT-22 was definitely a "value engineered" version. I understand that the swept back wings made the PT-22 easier to stall/spin if you got too slow, say on a turn to final. I wonder if that aerodynamic "refinement" was to produce a "better" trainer or just the result of a CG change from switching to the radial engine,

A guy in NC built a Ryan ST from scratch a while back. I've often thought it would be fun to convert a PT-22 to an ST with new wings and a Walther in-line engine.

Was it an ST-A or ST-M that showed up? The ST-M is more pared-back and spartan (being the military version). You don't need a lot of the prettiness for military use.

Not sure why you'd want to convert the PT-22 into an ST.

MIflyer said:
And apparently those airplanes have a power off sink rate somewhere between that of a Baldwin Piano and a Baldwin Locomotive.

A high sink rate, sure but not excessive. From memory, it wasn't too dis-similar to a Piper PA-38 as far as speeds and approach profile went. I've flown a primary trainer that with an engine out, the paddock you went for was just under the wing-tip, so was far worse than the PT-22.
Now, if you've been taught in a Stearman, then going from a bi-plane engine-out approach, which is very steep, nose-down to the PT-22 would be interesting. Not sure how much of the training changed.

Barrett · Jun 7, 2019

Reminds me: Flight tests of the Super Hornet revealed um exciting "excursions" in some high AOA, low airspeed configurations. The bubbas at Pax River realized that the computer modeling was, shall we say...flawed. In order to determine the optimum fix the guys experimented with different grits of sand paper glued to the airframe and eventually got the desired burble/flow/whatever.

Computers are way over-rate. But you knew that!

XBe02Drvr · Jun 7, 2019

Barrett said:
Computers are way over-rate. But you knew that!

G.I.G.O. Statistics aren't wrong, statisticians are. Same for computers and their geeks.

fliger747 · Jun 7, 2019

An essential of computer modeling is to have some "Ground truth", or "Air Truth" to validate it. Any kind of modeling relies on assumptions being correct. Sometimes they are not!

Very small aerodynamic corrections can have a big effect! The small change in the fillets by the cockpit was quite essential for the P-38. Having a nix of four and five blade propellers for four shafted US Fast Battleships was essential in reducing high speed vibration. The aerodynamics at high AOA gets very complicated!

pbehn · Jun 7, 2019

drgondog said:
I loaded that a long time ago during some discussions with Soren.

Turn aerodynamics is a complex discussion but consider thatALL WWII single engine fighters without contrarotating props have upwash on one wing and downwash on the other - causing the lift distribution to be different, particularly at near stall AoA. Secondly, wing elasticity comes into play in high G/High AoA flight, pointing to examination of aileron authority vs control reversal.

Power required varies directly with Weight times CD/CL to the CL 'break/stall' region. Draggy airplanes, all else being equal (and they never are), require more HP in a to maintain a comparable rate of turn.

Factors that are introduced for Drag are a.) increase in both pressure and parasite draq due to increase in CL, b.) increased Induced drag due to increase in CL and c.) Trim drag of deflected control surfaces to maintain turn dynamics. Mach number is a factor but only a brief one as energy is lost so very rapidly in a turn.

Prop efficiency is also a factor, particularly in the relatively low ranges of velocity.

I first became interested in aviation on the 25th anniversary of the Battle of Britain. My brother who was much older than me had been to an air display and returned with a pennant and some pictures of Spitfires and Hurricanes. Like any five year old I loved their curves and lines and in any case he was my big brother. Later I saw them fly in beautiful arcs and curves and later saw these curves in mathematics at school. Still later I worked with metals making them and testing them and learned how everything is "nominal" and from the nominal you have a minimum and a range of thickness and strength. The mathematics of aerodynamics has its own beauty, equations that explain relationships and limits. Then I realised, a Spitfire performing a 7G turn is trying to keep the weight of a fully loaded articulated lorry (truck) in the air on those beautiful slender wings, with the tolerances of all the engineering, something will go out of balance at the limit and when that limit is reached then things will go out of control very quickly. I am not surprised fighters would violently spin out of a turn, I am actually surprised they didn't violently do all sorts of things all the time in combat. Its a tribute to engineers that they didn't and don't. BTW at the specified maximum wing load how much was (is) the wing deformation on a P-51 from straight.

drgondog · Jun 8, 2019

pbehn said:
I first became interested in aviation on the 25th anniversary of the Battle of Britain. My brother who was much older than me had been to an air display and returned with a pennant and some pictures of Spitfires and Hurricanes. Like any five year old I loved their curves and lines and in any case he was my big brother. Later I saw them fly in beautiful arcs and curves and later saw these curves in mathematics at school. Still later I worked with metals making them and testing them and learned how everything is "nominal" and from the nominal you have a minimum and a range of thickness and strength. The mathematics of aerodynamics has its own beauty, equations that explain relationships and limits. Then I realised, a Spitfire performing a 7G turn is trying to keep the weight of a fully loaded articulated lorry (truck) in the air on those beautiful slender wings, with the tolerances of all the engineering, something will go out of balance at the limit and when that limit is reached then things will go out of control very quickly. I am not surprised fighters would violently spin out of a turn, I am actually surprised they didn't violently do all sorts of things all the time in combat. Its a tribute to engineers that they didn't and don't. BTW at the specified maximum wing load how much was (is) the wing deformation on a P-51 from straight.

I don't have the static test reports for the X73 at hand. That said, the original static testing on the X73 caused a failure at 12G near flap line and lower fuselage aft of wing (buckling) - which is why the first 10 ships were deemed unsuitable for combat operations (the Brits weren't disturbed). That said the two XP-51 were tested thoroughly in dive tests. The wing and empennage had incremental strengthening over different models with the two biggest changes being the A-36 wing, then the changes made via DFF, change in elevator incidence for the empennage as well as beefing up the ammo door covers.

Wing and empennage analysis/testing for asymmetrical loading was arcane as very little was known and practically applied for aeroelasticity issues. Absent iterative/relaxation methods to analyze joints/parts/torque boxes and the high speed computational capabilities emerging in the mid 60's, it was left somewhat to chance.

fliger747 · Jun 8, 2019

I had a friend who was a WWII SBD pilot and later was an engineer for Boeing and involved in the B47 program. He said about the SBD that he though the wings wouldn't flex an inch before breaking off. The B47 was a different cat, the shop guys on the floor used to working with B-17/B-29 etc kept shaking their heads over the rather elastic, log thin wings. A new design philosophy.

Power-On vs Power-Off Stall Speed

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