Aircraft Down Nylstroom

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Re: Aircraft Down Nylstroom

Unread post by TC » Sat May 18, 2019 2:18 pm

Spoke Eagle wrote:
Sat May 18, 2019 1:09 pm
I read on Google the Tomahawks have over effective rudders because Piper used an airfoil that would stall hard and spin easy to help CFI's during spin training. They also suffered twice the average stall/spin accidents. I'd rather not fly one IMHO.
I did a recent comparison (for a Trivia Quiz of all things) of the Beech Skipper vs the Tomahawk. They are virtually identical in all aspects, including having the exact same wing profile. With one difference...

The Tomahawk had wing ribs removed and holes drilled in the main spar AFTER certification, which resulted I’m the Tomahawk wing flexing more than the Skipper. They attribute this to the reason for the higher spin accidents.

Statistically the Tomahawk has 30% fewer accidents that the C150 per flight hour, but these accidents are 3 times more likely to be as a result of a spin.
My wife keeps saying I don't listen to her or something like that !?
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Re: Aircraft Down Nylstroom

Unread post by Chalkie » Sat May 18, 2019 2:48 pm

Spoke Eagle wrote:
Sat May 18, 2019 1:09 pm
I read on Google the Tomahawks have over effective rudders because Piper used an airfoil that would stall hard and spin easy to help CFI's during spin training. They also suffered twice the average stall/spin accidents. I'd rather not fly one IMHO.
TC. Dual typing...

I have many hours in a PA38 Tomahawk, all of them instruction. The PA38 had a rather abrupt stall and a wedge was added to the outboard leading edge of the wing to induce buffet; but as this was not too effective a second wedge was added to the inboard section. (On the fuel tank, IIRC) As a trainer the PA38 had a nice seating position above the main spar which gave the pilots good visibility; compared to the C152 where you sat on the 'floor' with a big sunshade above your head.

The stall speed of a Tomahawk clean was ONE Knot IAS more than a stall with full flap. This made the Tomahawk a bad trainer, in my opinion. However as a spin trainer the Tomahawk was EXCELLENT. The stall was abrupt (compared the the C152 which didn't really meet stall criteria.) so spin entry was assured if the aircraft was unbalanced. The spin happened slow enough for the instructor to patter the entry, the incipient stage and then the full spin stage.

However, and herein lay the problem for the inexperienced, the spin rate was slow. This meant that the recovery gyro B/A ratio was weak. A Tomahawk in a fully developed spin WILL NOT RECOVER WITHIN ONE TURN, but again as an instructing tool it was excellent. You could patter the student: Apply opposite rudder and release back pressure (allow elevator to find neutral) now wait... note the spin rate increases, the nose moves towards the landing gear and SNAP it is out of the spin. Then the normal lecture of recovery without overstressing the airframe etc...

Any reputation the Tomahawk might have due to spin problems was because the people concerned did not understand that a spin recovery in a Tomahawk happens slowly. Just wait, it WILL recover. The UK CAAB brought out a recommendation that the standard spin recovery was to apply stick forward, but I never found this necessary (assuming you have the height) just wait for 1 ¼ turns it WILL recover.

Excuse the thread drift but Stef needs to fly one to learn what a spin is really like.

The Traumahawk had an unfair reputation and this was due to the Piper sales department. A fly on the wall told me, they said sales were down. What can we do? And one clever guy said "fit a T-tail to all models..." The rest is history. The T-tail caused many AD's.
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Re: Aircraft Down Nylstroom

Unread post by jimdavis » Sat May 18, 2019 3:05 pm

Absolutely right Chalks. The Tomahawks did not have have spin recovery problems, it just highlighted instructor problems.

jim
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Re: Aircraft Down Nylstroom

Unread post by MLyons » Sat May 18, 2019 7:15 pm

The Tomahawk also was great at teaching the student to stay awake even in the cruise.
C152 is inherently stable in roll due to the high wing and pendulum effect, whereas in a Tomahawk, if the pilot got distracted from looking outside for any length of time, it would most likely be in a bank when he did eventually look outside.

Spinning a Tomahawk is very definitely a very "positive" experience in that you were 'positive' it has stalled, and you were 'positive' you were spinning - never had any trouble with the recovery personally, but heard some horror stories of developing into a bit of a flat spin with severe recovery difficulties when CG was a little too far on the aft side of the W/B envelope.

Loved the Tomahawk. Would buy another one in a flash at the right price.
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Re: Aircraft Down Nylstroom

Unread post by Chalkie » Sun May 19, 2019 9:15 pm

MLyons wrote:
Sat May 18, 2019 7:15 pm
- never had any trouble with the recovery personally, but heard some horror stories of developing into a bit of a flat spin with severe recovery difficulties when CG was a little too far on the aft side of the W/B envelope.
I will copy and paste from my post above:-
Chalkie wrote:
Sat May 18, 2019 2:48 pm
The stall speed of a Tomahawk clean was ONE Knot IAS more than a stall with full flap. This made the Tomahawk a bad trainer, in my opinion. However as a spin trainer the Tomahawk was EXCELLENT. The stall was abrupt (compared the the C152 which didn't really meet stall criteria.) so spin entry was assured if the aircraft was unbalanced. The spin happened slow enough for the instructor to patter the entry, the incipient stage and then the full spin stage.

However, and herein lay the problem for the inexperienced, the spin rate was slow. This meant that the recovery gyro B/A ratio was weak. A Tomahawk in a fully developed spin WILL NOT RECOVER WITHIN ONE TURN, but again as an instructing tool it was excellent. You could patter the student: Apply opposite rudder and release back pressure (allow elevator to find neutral) now wait... note the spin rate increases, the nose moves towards the landing gear and SNAP it is out of the spin. Then the normal lecture of recovery without overstressing the airframe etc...

Any reputation the Tomahawk might have due to spin problems was because the people concerned did not understand that a spin recovery in a Tomahawk happens slowly. Just wait, it WILL recover.
The UK CAAB brought out a recommendation that the standard spin recovery was to apply stick forward, but I never found this necessary (assuming you have the height) just wait for 1 ¼ turns it WILL recover.
Now I do not know what you and other pilots do; but when I went out to do spin training we never had baggage to move the CG aft as baggage can also fly about and cause damage.

The spin rotation rate in a Tomahawk is slow, the attitude is 'flat' compared to a C150/152 or PA18, I guess this all contributed to the 'horror stories.'

The aircraft was not the problem...
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Re: Aircraft Down Nylstroom

Unread post by jimdavis » Sun May 19, 2019 10:48 pm

I remember seeing a notice, possibly in the handbook, but I think on the panel, saying something like this:

SPIN RECOVERY
1. Throttle fully back & ailerons neutral
2. Use full opposite rudder, pause
3. Move the stick SMARTLY and FULLY forward. (Or words to that effect). Do you remember the wording Chalks?
4. When rotation stops...
5. ...
6. ...

I never found it necessary to move it SMARTLY and FULLY forward. SMOOTHLY and FIRMLY until rotation stops. I never really looked, but it seemed to stop spinning when the stick got about half-way forward - or maybe a bit further.

I always thought that "SMARTLY and FULLY forward" was a bit overkill, but maybe it was necessary under certain circumstances.

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Re: Aircraft Down Nylstroom

Unread post by Dragon » Sun May 19, 2019 11:02 pm

I am puzzled by the previous few posts. I firstly admit that I have only flown the Tomahawk once, but I flew her thoroughly and my impressions were lasting. What puzzles me is this: with 2 up and normal fuel to the GF from Grand Central I found the stall unmistakeable, the incipient assertive, the spin started slowly and shallow I will give you, but wound up quite quickly when held in the spin and dropped quickly into an unusually steep nose attitude for a spin. To this day I haven’t found an aircraft that spins as steep as that Tomahawk did that day. And the rotation really wound up, even more so during recovery. The other thing that I liked about the spin was that the instructor flying with me demonstrated to me that it was pretty intolerant of incorrect techniques, and wouldn’t recover for example if recovery was out of sequence making it a great training aircraft (in my opinion)- forces correct technique to be learned.

So when I remember a fully fledged Tomahawk spin, I think more of a “Downward Charlie” than a lazy flattish spin. I am wondering if other instructors are recovering very early on before she has dropped her nose and wound up, or if our Tomahawk that day had an idiosyncratic spin? Anyone?
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Re: Aircraft Down Nylstroom

Unread post by Dragon » Sun May 19, 2019 11:31 pm

jimdavis wrote:
Sun May 19, 2019 10:48 pm
I remember seeing a notice, possibly in the handbook, but I think on the panel, saying something like this:

SPIN RECOVERY
1. Throttle fully back & ailerons neutral
2. Use full opposite rudder, pause
3. Move the stick SMARTLY and FULLY forward. (Or words to that effect). Do you remember the wording Chalks?
4. When rotation stops...
5. ...
6. ...

I never found it necessary to move it SMARTLY and FULLY forward. SMOOTHLY and FIRMLY until rotation stops. I never really looked, but it seemed to stop spinning when the stick got about half-way forward - or maybe a bit further.

I always thought that "SMARTLY and FULLY forward" was a bit overkill, but maybe it was necessary under certain circumstances.

jim
Jim “Smartly” is only sometimes a good idea- when specifically requested by the handbook, but “Fully” is always a good idea (esp if you fly multiple types) unless you know the aircraft very well and know better. I don’t know exactly what the wording on that notice said, but I have to say that there is barely an aircraft that has been made that will not recover to that formula provided “the stick is progressively moved forwards and then held fully forward until the rotation has stopped”.

This makes the procedure work for aircraft that will recover either:
1 with the stick released from full back-stick
2 with the stick in neutral
3 with the stick slightly forwards
4 with the stick fully forwards

The aircraft recovers when it is happy to. So take a few seconds to push the stick forwards (not 10s, like maybe 2-3s). You won’t stall the elevator, and some aircraft will recover without too much nose down input. Those that need it still get it. And even the C150 is putty in the hands. For those very few aircraft with unusual stall recoveries, and I define that as any aircraft that doesn’t recover to what I have said here, will have a specific procedure highlighted in the handbook. Most recovery failures are from people not positioning the stick far enough forwards, and this solves that one for ever.
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Re: Aircraft Down Nylstroom

Unread post by aviasiecom » Mon May 20, 2019 6:46 am

Spins in the Tomahawk
Recovery:
https://ramaviation.com/wp-content/uplo ... 38-POH.pdf
Bladsy 4-24. Paragraaf 4.43.

Hier's Eddiie:
https://www.youtube.com/watch?v=X0h1nG_ibdQ

En NASA:
https://www.youtube.com/watch?v=xzFgqtPVCZ0

Only 300 hrs and counting in the Tomahawk, so can't quote my own experience.
Creston
P.S. Still looking for evidence of which ribs were removed after certification, as often quoted on line.
"Trap oppie bal en hou hom in die middel" (unrelated to spin recovery).
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Re: Aircraft Down Nylstroom

Unread post by aviasiecom » Mon May 20, 2019 7:06 am

Follow up post.
Jim Patton, test pilot for the Tomahawk at NASA in Langley, fascinating life.
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Re: Aircraft Down Nylstroom

Unread post by Chalkie » Mon May 20, 2019 8:21 am

jimdavis wrote:
Sun May 19, 2019 10:48 pm
I remember seeing a notice, possibly in the handbook, but I think on the panel, saying something like this:

SPIN RECOVERY
1. Throttle fully back & ailerons neutral
2. Use full opposite rudder, pause
3. Move the stick SMARTLY and FULLY forward. (Or words to that effect). Do you remember the wording Chalks?
4. When rotation stops...
5. ...
6. ...

I never found it necessary to move it SMARTLY and FULLY forward. SMOOTHLY and FIRMLY until rotation stops. I never really looked, but it seemed to stop spinning when the stick got about half-way forward - or maybe a bit further.

I always thought that "SMARTLY and FULLY forward" was a bit overkill, but maybe it was necessary under certain circumstances.

jim
It would seem that mods need to move this discussion to a separate thread as it is perhaps not applicable to this accident.

Jim, the 'Pause' after full rudder application does not apply to the Tomahawk as it has a T-tail and all the rudder is exposed to the relative airflow for spin recovery.

I too never found it necessary to move the stick fully forward's to un-stall the wing and anyone who does this will need to release the pressure as spin rotation increases (sign of recovery) as the aircraft normally recovers with a steep down nose attitude and over stressing during the dive is a real potential problem.
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Re: Aircraft Down Nylstroom

Unread post by Chalkie » Mon May 20, 2019 8:38 am

Dragon wrote:
Sun May 19, 2019 11:02 pm
I am puzzled by the previous few posts. I firstly admit that I have only flown the Tomahawk once, but I flew her thoroughly and my impressions were lasting. What puzzles me is this: with 2 up and normal fuel to the GF from Grand Central I found the stall unmistakeable, the incipient assertive, the spin started slowly and shallow I will give you, but wound up quite quickly when held in the spin and dropped quickly into an unusually steep nose attitude for a spin. To this day I haven’t found an aircraft that spins as steep as that Tomahawk did that day. And the rotation really wound up, even more so during recovery. The other thing that I liked about the spin was that the instructor flying with me demonstrated to me that it was pretty intolerant of incorrect techniques, and wouldn’t recover for example if recovery was out of sequence making it a great training aircraft (in my opinion)- forces correct technique to be learned.

So when I remember a fully fledged Tomahawk spin, I think more of a “Downward Charlie” than a lazy flattish spin. I am wondering if other instructors are recovering very early on before she has dropped her nose and wound up, or if our Tomahawk that day had an idiosyncratic spin? Anyone?
Pitch attitude as remembered is a subjective thing. In my post I said the attitude is 'flat' this is as compared to a C150/152 and PA18. I have spun the PA38 with up to 6 turns fully established (excluding the incipient stage) but instructed all students not to exceed 3 turns; because, yes, it does wind up (as I pointed out, making it a good training tool) and end up in a steep dive in the recovery.

In the Wits Flying Club we had two PA38's KHV and KHY. KHY was buckled in a hard landing which affected the wing incidence. (The ailerons had large tabs fitted, the one bent up, the other bent down to make the aircraft fly straight.) This aircraft would only spin in one direction and would enter a spiral dive if you tried to spin it the other direction.

As for a high spin rotation rate: go spin an RV-6 it blurrs the horizon...
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Re: Aircraft Down Nylstroom

Unread post by MLyons » Mon May 20, 2019 8:41 am

Chalkie wrote:
Sun May 19, 2019 9:15 pm
The aircraft was not the problem...
Truth be told, Chalkie, the aircraft is very seldom the problem.
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Re: Aircraft Down Nylstroom

Unread post by Dragon » Mon May 20, 2019 11:47 am

aviasiecom wrote:
Mon May 20, 2019 6:46 am
Spins in the Tomahawk
Recovery:
https://ramaviation.com/wp-content/uplo ... 38-POH.pdf
Bladsy 4-24. Paragraaf 4.43.

Hier's Eddiie:
https://www.youtube.com/watch?v=X0h1nG_ibdQ

En NASA:
https://www.youtube.com/watch?v=xzFgqtPVCZ0

Only 300 hrs and counting in the Tomahawk, so can't quote my own experience.
Creston
P.S. Still looking for evidence of which ribs were removed after certification, as often quoted on line.
"Trap oppie bal en hou hom in die middel" (unrelated to spin recovery).
Thank you for this extremely informative post. It seems my recollection is correct and as you could see from the description in the handbook of the steep spin and the profound difference between the 4 turn and 6 turn spin (and difference in recovery) in the excellent NASA video, the Tomahawk starts with a benign spin but it is not yet stable and soon steepens and believe me by 8 or 10 rotations you are pointed at the ground and spinning like a top, with recovery needing to be that much more precise.

Jim I think their biggest reason for using the word “SMARTLY” forward here is to avoid people fiddling about and not getting the stick to the fully forward position which is where they want it (also it saves a second on this particular aircraft). Chalkie is correct about the rudder pause not being required because of the T tail. I would still use it to keep my universal spin recovery procedure intact, because it doesn’t hurt anything (except use up a second or two- so I reserve the right to jettison it if I am low on altitude) and I can continue to use my spin procedure on almost every aircraft on the planet.
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Re: Aircraft Down Nylstroom

Unread post by Dragon » Mon May 20, 2019 12:40 pm

Chalkie wrote:
Mon May 20, 2019 8:38 am

Pitch attitude as remembered is a subjective thing. In my post I said the attitude is 'flat' this is as compared to a C150/152 and PA18. I have spun the PA38 with up to 6 turns fully established (excluding the incipient stage) but instructed all students not to exceed 3 turns; because, yes, it does wind up (as I pointed out, making it a good training tool) and end up in a steep dive in the recovery.

As for a high spin rotation rate: go spin an RV-6 it blurrrs the horizon...
Chalkie thank you for your post it is always good to speak to someone with lots of instruction time on the aircraft.

I think this has turned out to be about the nature of the Tomahawk accelerating her spin. She starts off fairly flat esp in incipient phase and then gradually keeps getting steeper, so it all depends on when you recover. If you recover at 3 or maybe 6 turns you might say she is lazy and flatter than a C150 and PA18, but if you let her wind up to 8 or 10 spins, you are in for a very steep wild and exciting ride, and by the way the recovery also takes that much longer - about a 3turn recovery or so at an even more accelerated and even steeper attitude, probably vertical. You will have a very different memory. By the way I have spun the RV, and again perhaps it was because we went 8-10 rotations in the Tomahawk, but the Tomahawk rotation was faster in my memory, just very different. Most of the Tomahawk rotation is in the rolling plane because the nose is pointed at the ground, while in the RV there is much more yawing going on and at least you can see the horizon to get it to blur!
Chalkie wrote:
Mon May 20, 2019 8:38 am

In the Wits Flying Club we had two PA38's KHV and KHY. KHY was buckled in a hard landing which affected the wing incidence. (The ailerons had large tabs fitted, the one bent up, the other bent down to make the aircraft fly straight.) This aircraft would only spin in one direction and would enter a spiral dive if you tried to spin it the other direction.
It is always interesting how each aircraft has its own spin character. I spun KHP from Avex Air by the way. As for your bent aircraft: With big aileron tabs it is almost like spinning with inspin aileron or outspin aileron. Which usually gives a very slow flat spin outspin and a very steep wound-up spin inspin, which brings the question, were the instructors a hundred percent sure it was a spiral dive (speed increasing) and not a very steep spin mode (which I promise has exactly the same if not a worse attitude)?

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