Poor Aircraft Design

[Henning]

I thought the Traumahawk was designed specifically so that it COULD be spun, and easily.

Here's the deal best as I know it, it may be flawed as it's all a collection of poor info samples at best; so take it for that.

The T-Hawk as designed and tested was OK to be spun. The T-Hawk as built if I understand dunno is built with less ribs in the wing and can be oil canned in a spin.

 

[DouglasBader]

The tomohawk was one of the few aircraft that have ever had to undergo retesting and recertification. The problem was the original airfoil and the ability of the aircraft to change geometry under a load. It can spin fine a hundred time and become unrecoverable on the 101st, or the 500th. One simply doesn't know.

The following collection of information, statements, and articles may be of some interest on the subject. It includes statements from some well known authorities on spinning light aircraft (including several authors of books on the topic):

http://www.ozaeros.flyer.co.uk/tomahawk/tomahawk.htm

 

[Henning]

Per Wikipedia:

[For 1982] Cadillac introduced a new aluminum-block 249-cubic-inch 4.1-liter HT series V8 engine to replace the V8-6-4. The new power plant featured a closed-loop digital fuel injection system, free-standing cast-iron cylinders within a cast-aluminum block, and was coupled with a 4-speed automatic-overdrive transmission.
​

More ...

The HT4100 was prone to failure of the intake manifold gasket due to scrubbing of the bi-metal interface, aluminum oil pump failure, cam bearing displacement, weak aluminum block castings and bolts pulling the aluminum threads from the block. It may not have been the most successful engine to sit under the hood of a Cadillac, but potential buyers were no more satisfied with the other two engines available at the time, the V8-6-4 and the Oldsmobile 5.7 L Diesel. Reliability issues soiled the reputation of the HT4100.
​

The 368-cu-in V8-6-4 was only on the '81 model. Its main problem was in the electronic controller, not the engine itself.

Huh, don't even recal that engine. Personally I liked the V8-6-4, I drove around a Coupe DeVille with one and would get 27mpg down the highway. I drove that car for a while and had no trouble. We used to get the V8-6-4 and GM Diesel full size fully loaded cars from the auction for dirt, get a 403 Olds to replace and make a couple grand easy for a few days of parts swapping.

 

[kyleb]

The tomohawk was one of the few aircraft that have ever had to undergo retesting and recertification. The problem was the original airfoil and the ability of the aircraft to change geometry under a load. It can spin fine a hundred time and become unrecoverable on the 101st, or the 500th. One simply doesn't know.

The following collection of information, statements, and articles may be of some interest on the subject. It includes statements from some well known authorities on spinning light aircraft (including several authors of books on the topic):

http://www.ozaeros.flyer.co.uk/tomahawk/tomahawk.htm

As an ex-tomahawk owner, I have gone through the NTSB reports on tomahawk fatalities, paying particular attention to stall/spin accidents. IIRC, 12-15 years ago, there were 50 something on the NTSB website. The vast, vast majority of them were typical stall/spins like you'd see from a Cub. Stall/spin on base to final. Low altitude maneuvering, etc. NOT "Intentionally entered a stall at 5,000' and couldn't recover." At the time, there may have been one accident which fit that profile in the browsable files.

One too many, but the dark tale of intentional spins in Tomahawk going all the way to the ground is not confirmed by the NTSB database.

What you will find with the Tomahawk is an aircraft that stalls several knots faster than a C-152. I suspect that was the causal factor for many of the stall/spins which began at pattern height or lower.

 

[flightwriter]

Huh, don't even recal that engine.

The HT4100 gets a bad rap, and deservedly so, but it did eventually lead to the 4.5L and later 4.9L V8s. They had their minor problems as well, but not nearly as many as the 4100 did... and not as many as the 4.6L Northstar that replaced the pushrod V8s did.

Despite having only 150 hp, the 4.5 in my grandfather's 1988 Sedan de Ville pulled strongly past 90K without any major problems, which was fairly rare for a GM engine in the 1980s.

 

[dukeblue219]

Im calling shenanigans on this. 18,482 were built, assuming a crew of 7 that would mean 2142 B24's crashed in the US which does not seem reasonable.

From Wikipedia entry on the Army Air Forces casualties in WWII (yes, they have a good citation for these numbers):

35,946 non-battle deaths included 25,844 in aircraft accidents, more than half of which occurred within the Continental United States

So, we have somewhere on the order of 15,000 aircraft accident deaths in the US during the war. Perhaps that is where the number came from... certainly not from any specific aircraft type.

 

[DouglasBader]

As an ex-tomahawk owner,

How many spins did you do in the Tomahawk?

You may not have think the airplane merited it, but the FAA certainly did when it undertook recertification trials on the airplane...one of the very few times such has ever been done to an aircraft in the USA. The FAA isn't the only country or authority to do it, either.

Did you visit the link provided?

 

[zaitcev]

I heardMcCulloch J-2 took every record in crashes.

Tomahawk bashing and its spin story is only marginally better than the bogus stuff that Cirrus-haters push. I remember we taked a Skipper once and Jesse said he'd take PA-38 over it easily, especially later models.

 

[DouglasBader]

The various aviation authorities that required it to revisit certification were equally ignorant, then? Everyone, every nation, every agency, every certification authority, every spinning authority, and more who found the aircraft to merit further investigation, and who has genuinely determined that the aircraft did have unique issues simply doesn't know what you know? You know more than a lot of other people, it seems, and given that many of them are authorities in their field, that makes you one smart cookie.

Everyone is a "hater" and ignorant on the subject, but you. Got it.

 

[kyleb]

How many spins did you do in the Tomahawk?

You may not have think the airplane merited it, but the FAA certainly did when it undertook recertification trials on the airplane...one of the very few times such has ever been done to an aircraft in the USA. The FAA isn't the only country or authority to do it, either.

Did you visit the link provided?

What did the FAA conclude when they reviewed the Tomahawk? What changes or limitations were put in place? None.

Regarding the link, it contained a lot of back and forth, concentrating on the stall recovery technique for the Tomahawk and the fact that it takes up to 1.5 turns to recover from a spin, according to Piper. There was nothing definitive there, and at the end, the site's author was disappointed in whatever AOPA wrote about the Tomahawk, because it didn't agree with his opinion.

Whether I spun the aircraft or not is immaterial. My one data point would be worthless, wheras the archive of accidents on the NTSB website paints a picture that I find pretty clear.

At the end of the day, I've done the research through the NTSB website to convince myself that Tomahawks don't spin into the ground during spin training. They spin into the ground because someone stalled them in an uncoordinated manner at low altitude. If you doubt this, pull up the NTSB accident reports yourself. The pattern will emerge very quickly.

 

[Pilawt]

I heardMcCulloch J-2 took every record in crashes.

Ah, yup.

It was advertised as combining the best features of fixed-wing and rotary-wing, when in fact it was the worst of both. With a 180-hp Lycoming it could carry two people and a toothbrush about 150 miles at 95 mph. Into a gentle breeze it could spot-land, but needed a considerable distance to accelerate out of ground effect on takeoff. A competent pilot in a Cessna 150 could just about duplicate the short-field takeoff performance of a J-2.

On takeoff the aircraft had to be stopped in position on the runway for 45 seconds while the rotor clutch was engaged and the rotor spun up to takeoff rpm (LGB tower hated us and relegated us to a parallel taxiway for takeoffs). As soon as the takeoff roll began the rotor clutch was disconnected and the rotor was in free-wheeling autorotation for the duration of the flight. It could not hover -- it could "fly" at zero airspeed, but would be going straight down - in a level attitude - at an impressive rate.

The POH prohibits takeoff above 4,000' pressure altitude and any operation above 8,000' pressure altitude. Operations on unpaved surfaces or in crosswind were strongly discouraged. Noise level inside and out was horrendous.

May 5, 1971 -- that's me on the left. I was getting post-solo dual instruction in the beast when this happened. It was the third such landing-rollover accident of the six J-2s that had been built to that time -- one of them by a factory test pilot (on that one the NTSB report cites "inadequate design"). FAA eventually required modification of the nosegear, but when I later flew a modified J-2 I didn't notice much improvement.

 

[DouglasBader]

Whether I spun the aircraft or not is immaterial. My one data point would be worthless, wheras the archive of accidents on the NTSB website paints a picture that I find pretty clear.

It's very material, because you made it so. You were quick to lead with the fact that you were a Tomahawk owner. How does being an owner apply? It doesn't: your qualification is that you never spun the airplane, but read about it.

Conversely, whereas the Tomahawk never met the proper spin criteria from the outset and was never properly tested or vetted (just as the Cirrus was never taken to an occupied touchdown after a parachute deployment during testing and certification), it needed a complete re-evaluation.

Test personnel, instructors who specialized in spin certification and training, industry safety specialists and others all point to the oil canning that takes place, the airfoil deformation, the accelerated spinning and unpredictable spin characteristics, the flattening of the spin early in the spin and just past the incipient phase, difficulty in recovery, and numerous other factors as undesirable characteristics of the airplane when spinning.

Spin entry is inconsistent, often rapid, and recovery also inconsistent and imprecise. The airplane was involved in more than double the rate of stall spin fatalities and mishaps as the Cessna 150, although far more 150's were in use and far more hours were flown in the 150's. The FAA saw fit to issue the AD for stall strips on the wings, and required the recertification as the airplane had never met certification criteria initially, and the high mishap rate and stall-spin rate demanded further attention.

 

[Old Geek]

Benson Gyrocopter killed quite a few pilots....

 

[DavidWhite]

I heardMcCulloch J-2 took every record in crashes.

Tomahawk bashing and its spin story is only marginally better than the bogus stuff that Cirrus-haters push. I remember we taked a Skipper once and Jesse said he'd take PA-38 over it easily, especially later models.

By bogus you mean ****-poor fuel tanks that were drawn up and thought a good idea by a family of lemurs???

Wait......

Perhaps I am giving lemurs too little credit. The Cirrus Sr22 Had 18 accidents last year, and 1 incident. Of the accidents, 9 were fatals. Feel free to post statistics to the contrary. The grand totals for the SR22 are 55 fatals, and 72 nonfatals, not counting the one last week.

The grand total for the Cessna 210 is 2430 nonfatal, and 640 nonfatal.

Anyways, take it for what it is - the truth. I can see how these numbers clearly show that the Cirrus is in fact the safest airplane around, just like the owners claim. I wonder how many of the nonfatal Cirrus crashes would have been fatals without the chute.........

I don't think any of those 210 crashes were saved by a parachute.

 

[Skylane81E]

By bogus you mean ****-poor fuel tanks that were drawn up and thought a good idea by a family of lemurs???

Wait......

Perhaps I am giving lemurs too little credit. The Cirrus Sr22 Had 18 accidents last year, and 1 incident. Of the accidents, 9 were fatals. Feel free to post statistics to the contrary. The grand totals for the SR22 are 55 fatals, and 72 nonfatals, not counting the one last week.

The grand total for the Cessna 210 is 2430 nonfatal, and 640 nonfatal.

Anyways, take it for what it is - the truth. I can see how these numbers clearly show that the Cirrus is in fact the safest airplane around, just like the owners claim. I wonder how many of the nonfatal Cirrus crashes would have been fatals without the chute.........

I don't think any of those 210 crashes were saved by a parachute.

No but I bet a good number of the fatals could have been.

 

[DouglasBader]

Benson Gyrocopter killed quite a few pilots....

No. Pilots killed themselves. They merely misued the Bensons (and other gyrocopters) to do it.

Bunting takes most of them, and it's a known phenomenon. We can't really compare homebuilt plans-built experimentals to the world of certified aircraft, can we?

As for comparing a Cessna 210 to a Cirrus, how many hours have the fleet of over nine thousand 210's flown, safely? How many hours have the fleet of Cirrus flown, and how large the fleet?

By and large, most of the parachute deployments in the cirrus have been gimmick deployments; situations into which the users placed themselves based on the false confidence of the parachute. Night IMC in a thunderstorm over the rockies, a pilot deploys CAPS and miraculously survives against all odds, earning scars in a battle in which he should never have fought. The list goes on ad infinitum, to include multiple failures of the CAPS system.

Whereas in the 210 one must land the aircraft, in the CAPS system in the Cirrus one has the option of destroying the airplane to save one's self from one's carelessness and stupidity. Does losing an aileron in flight merit the deployment? Perhaps, but then one must ask why the control surface wasn't properly inspected before the flight begin, and of natural consequence ask how many cirrus pilots were lulled into doing things they ought not by having the magic red handle to pull?

More importantly, one ought to ask how many of those individuals, mostly all inexperienced pilots, would have ever put themselves in such precarious positions had they not had the gimmick there to tempt them in the first place. Statistics lie, especially as the colors are cast in different light.

 

[zaitcev]

As for comparing a Cessna 210 to a Cirrus, how many hours have the fleet of over nine thousand 210's flown, safely?

Since you evidently do not know the history of David's research, you're missing the spin he's trying to apply. The point was to exclude the fleet hours by comparing the ratio of fatals to non-fatals. When he counted everything, it turned out that Cirrus is just as safe or safer than, for example, V35 - in that you have better chances to survive a crash in Cirrus despite all the scaremongering about its tanks. Unsatisfied with facts that he uncovered, David then found an airplane that has a better ratio for whatever reason, that being a 210. Now he's going to mention the 210 whenever the subject turns to Cirrus.

 

[kyleb]

It's very material, because you made it so. You were quick to lead with the fact that you were a Tomahawk owner. How does being an owner apply? It doesn't: your qualification is that you never spun the airplane, but read about it.

Conversely, whereas the Tomahawk never met the proper spin criteria from the outset and was never properly tested or vetted (just as the Cirrus was never taken to an occupied touchdown after a parachute deployment during testing and certification), it needed a complete re-evaluation.

Test personnel, instructors who specialized in spin certification and training, industry safety specialists and others all point to the oil canning that takes place, the airfoil deformation, the accelerated spinning and unpredictable spin characteristics, the flattening of the spin early in the spin and just past the incipient phase, difficulty in recovery, and numerous other factors as undesirable characteristics of the airplane when spinning.

Spin entry is inconsistent, often rapid, and recovery also inconsistent and imprecise. The airplane was involved in more than double the rate of stall spin fatalities and mishaps as the Cessna 150, although far more 150's were in use and far more hours were flown in the 150's. The FAA saw fit to issue the AD for stall strips on the wings, and required the recertification as the airplane had never met certification criteria initially, and the high mishap rate and stall-spin rate demanded further attention.

Are you arguing that the aircraft behaves differently in a spin than other aircraft? I won't argue that, all aircraft exhibit different spin behaviors. Heck, the designer of my RV-6 doesn't recommend spins in the type.

But, if you're arguing that the aircraft has a history of entering unrecoverable spins from reasonable altitudes, that argument doesn't stand up to an objective review of the facts.

 

[SCCutler]

The HT4100 gets a bad rap, and deservedly so, but it did eventually lead to the 4.5L and later 4.9L V8s. They had their minor problems as well, but not nearly as many as the 4100 did... and not as many as the 4.6L Northstar that replaced the pushrod V8s did.

Despite having only 150 hp, the 4.5 in my grandfather's 1988 Sedan de Ville pulled strongly past 90K without any major problems, which was fairly rare for a GM engine in the 1980s.

I had a 1990 DeVille with the 4.5; sold it to my bother in law with something like 180,000 miles, he sold it by the side of the road a couple of years later at around 260,000 miles, and we know it ran on, because it was used in an armed robbery as a getaway car about a year later (guy never changed the title).

The 4.1 was gosh-awful, but the 4.5 and the 4.9 which followed were excellent mills.

 

[wabower]

I had a 1990 DeVille with the 4.5; sold it to my bother in law with something like 180,000 miles, he sold it by the side of the road a couple of years later at around 260,000 miles, and we know it ran on, because it was used in an armed robbery as a getaway car about a year later (guy never changed the title).

The 4.1 was gosh-awful, but the 4.5 and the 4.9 which followed were excellent mills.

Are there any old Caddies that you haven't owned?:wink2:

 

[DavidWhite]

Since you evidently do not know the history of David's research, you're missing the spin he's trying to apply. The point was to exclude the fleet hours by comparing the ratio of fatals to non-fatals. When he counted everything, it turned out that Cirrus is just as safe or safer than, for example, V35 - in that you have better chances to survive a crash in Cirrus despite all the scaremongering about its tanks. Unsatisfied with facts that he uncovered, David then found an airplane that has a better ratio for whatever reason, that being a 210. Now he's going to mention the 210 whenever the subject turns to Cirrus.

If you could point me to a place where I could find fleet hours, feel free. Accusing me of not including information is pretty stupid. You need to know what the hell you are talking about if you are going to accuse me of trying to spin something. It's no secret I don't like Cirrus, but the numbers I just posted are fact and not fiction, as much as it obviously pains you to acknowledge that.


Just an FYI the V35 has 158 fatals and 344 nonfatals.

 

[Ted]

Good question. I suspect the FAA certification process categorically eliminates a lot of bad designs, at least since post WWII.

It is still possible to certify something that is a bad design or unsafe. However, there is a good amount of truth to this. The bar that one must jump in order to produce a certified aircraft is high enough that most folks won't try to certify something that isn't going to be safe and marketable.

 

[DavidWhite]

The bar that one must jump in order to produce a certified aircraft is high enough that most folks won't try to certify something that isn't going to be safe and marketable.

Or atleast one of the two.

 

[Ted]

Are there any old Caddies that you haven't owned?:wink2:

Apparently his family still owns all of them!

 

[Pilawt]

Despite having only 150 hp, the 4.5 in my grandfather's 1988 Sedan de Ville pulled strongly past 90K without any major problems, which was fairly rare for a GM engine in the 1980s.

The 4.5 in my '89 SDV went 135K trouble-free before I sold it.

 

[DouglasBader]

The point was to exclude the fleet hours by comparing the ratio of fatals to non-fatals. When he counted everything, it turned out that Cirrus is just as safe or safer than, for example, V35 - in that you have better chances to survive a crash in Cirrus despite all the scaremongering about its tanks.

The fleet hours and numbers can't be excluded; otherwise, the data is meaningless.

A fleet of 20,000 that flies 50,000 hours a year and has ten incidents is nothing compared to a fleet of two that flies 10 hours a yea and has lost one aircraft. One could try to exclude the details and suggest that the aircraft from the smaller category is safer, because it's had less aircraft go down. Given that it's suffered a 50% fleet failure, that's not such a good statistic. Factoring in the hours, it gets even worse.

One can't exclude the hours or fleet size. One shouldn't ignore the demographics of the pilots involved, either.

Are you arguing that the aircraft behaves differently in a spin than other aircraft?

I'm not arguing at all, as there's no argument. It's a fact.

But, if you're arguing that the aircraft has a history of entering unrecoverable spins from reasonable altitudes, that argument doesn't stand up to an objective review of the facts.

Again, there's no need for argument. The Tomahawk is more susceptible to spins, and whether it's instructors having difficulty at "reasonable altitudes," or spins occurring in the real world where they are occurring, causing the fatalities they're causing (because the airplane is spin-prone, has unpredictable spin entry characteristics, rapid departure characteristics, and let's not forget: changes it's geometry and airfoil during a spin), the fact is that it has a history of entering unrecoverable spins and killing people.

 

[Jaybird180]

 

[Geico266]

The 2 cycle engine, 2 axis ultra lites were widow makers in their day. Easy Riser was a classic. Quick Silver 2 axis was another.

http://m.youtube.com/#/watch?desktop_uri=/watch?v=E8xF-myj0gM&v=E8xF-myj0gM&gl=US

http://www.quicksilveraircraft.com/sprint.htm

 

[Mason]

I've no idea why, but I took a chance on another Caddy, an '89. It was great. Loved that car.

I had an '89 Fleetwood that I bought used and drove it up to 180k miles, quite a nice boat and very reliable.

 

[tonycondon]

there are tons of one-off and experimental sailplane designs that have been built to test out certain theories and advance the general state of the art. Some very interesting, such as this one that I found the other day: http://en.wikipedia.org/wiki/Kesselyák_KM_400

My opinion is that true poorly designed aircraft don't get built in large numbers because they are, well, poorly designed and they show it in operation or during certification attempts.

 

[zaitcev]

My opinion is that true poorly designed aircraft don't get built in large numbers because they are, well, poorly designed and they show it in operation or during certification attempts.

There may be circumstances. Ilyushin Il-2, the most-built warplane in history, had significant handling problems due to the center of mass creeping rearward as new equipment was added (in particular, the rear gunner with the UBT gun, but also DAG-10 etc.). Basically, if you stalled it, it was not recoverable, because the tail stalled first. Starting in 1943 they added new wings, sweeping back like on DC-3, which helped quite a lot and reduced non-combad deaths. All in all, 35,000 were built and they dealt a significant damage to Germans. Unfortunately, I don't have good data on the non-combat deaths in the type, I only heard that they were significant.