Why is the PA28-161 not cleared to spin?
 

The original PA28-140 was cleared for spinning, but the later Warrior with the tapered wing design was not, why is that?

(I understand the wing design has something to with it)

A marked limited tolerance to negative g? (serious lack of inbuilt chunkiness in the lamina-flow versus the slab wing?) - when I used to fly sundry 161s and 181s I always wondered what abuse might have been dished out unseen/untold by more adventurous renters before me.

Can't recall any break up reports but I guess someone will point us in the right direction.

IIRC it's a C of G issue.

Even the -140 Cherokee has to be loaded within a tighter CG envelope (was thar called Utility) for spinning.

It is a c of g issue, but also the warrior has quite a comparatively small rudder and short fuselage for the wing area. Although it is is possible to spin a warrior, it is not cleared to do so because the chances are you will [B]NEVER[B] recover.
So promise you will NEVER try it!

Yes, it has something to do with wing design. The tapered wing has less drag in autorotation. That is why the spin will be flatter and the horisontal stabilizer shadows the rudder so much, that it possibly has not the power for recovering the plane from the spin. So do not try!

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I'm puzzled by that - how did it get an Airworthiness Certificate?

Good question!

Surely with so many modern GA aircraft not being cleared to spin spinning is going to become a lost art.

Even if "not cleared to spin" surely an aircraft should be recoverable if it does?

The "not cleared" is presumably because, for one or many good reasons, it's not a good idea.

But an aircraft that will kill if spun, intentionally or not, is hardly airworthy, I would have thought.

I did try to spin a Cherokee 140, some years ago, but could not achieve more than a very steep spiral dive, really, even by slowing to almost the onset of a stall, then chopping the power, heaving back hard with the elevator and giving it full rudder, and holding that pose for a while. The problem was then the speed which increased rapidly in the spiral dive that eventually developed, and resuming level flight before it increased any more, without breaking something. I think there was a spring connection between rudder and aileron to make it as much like a car as possible, which didn't help.

Is a Warrior like that?

It isn't that robust either. There is a list of permitted manouvres somwhere and as I recall the most radical was a chandelle.

OK - I'm a simple controller with a lapsed PPL but as I understand things any aircraft will spin if placed into the appropriate circumstances. Those that are not cleared for spinning simply cannot be recovered using commonly available techniques and so for certification it is declared as not-spinable....just as a PA28 is not certified for flight at 300kts, because it will probably fall apart.

While we're on type here, there is a limitation in the POH that i would lik to see discussed.

"use of flap 25 during take-off is prohibited for all commercial operations and is not recommended for private operations"

Why do they make a different rule for each as the weight the aircraft can carry for either operations wil be the same?

Seems daft to to prohibit it for both.

I am especially keen on comments for the "dump the extra flap to get in to ground efect" contingent.

Regards

D'vay

I've always been taught that one uses flaps 0 for tarmac and 25 for grass. The rotate speed is slightly higher with no flaps, probably 65 knots as oppposed to 55.

But why did the PA28 loose the ability to spin, it just seems like a rather retrograde step.

The aircraft will spin, and I have done so a few times for flight testing, along with the 181 and the Arrow III and IV. The problem as I understood it (way back when) was two fold. Firstly, when the aircraft is really 'wound up' the 'break out' forces can be 'misinterperated' and while you might think you have full control deflection, in fact the controls come up against a small aerodynamic 'stop' and a greater control force is then required to 'break out' of the spin. This was particularly so with a rear limit C of G. It was thought that some pilots might not recover because they would be lead to believe they had applied full recovery action when in fact they had not.
It had not escaped the notice of Piper, at the time, that these aircraft were being loaded without any regard for the C of G or calculations to confirm the aircraft was within the C of G limits. ie. four thumping great chaps and a big old dinghy and baggage in the back. As the aircraft was not intended for aerobatics, the second factor was thus one of 'Product liability', so it was easier to just prohibit this maneauvre. At the time Cessna had just been taken to court under the product liability issue and lost to a man who ran out of fuel and crashed. His argument was that nowhere in the flight manual (aircraft handbook) did it actually say that you had to put fuel in it!!!

Its all down to the wing shape, I spun slab a wing PA-28 in my training, you really need to force them to fully develop, the CFI i had managed to spin a warrior but said it was a little "tricky" on recovery!

The 140 Cherokee had a shorter fuselage and a different wing. It actually started life as the Thorpe Sky Scooter and was a two seater. Piper initially made the PA 160 a full four seater, the wing was diferent again, having no 'wash out'. When the PA 28-140 was concieved it was a 2+2 having a limit of only 200lbs on the rear seats, and a wing with 'wash out'. How many times have you seen 4 adults climb out of one? The aircraft was certified in two categories 'Normal' and 'Utility'. I've forgotton which one is which but I think that you could only spin it in the 'Utility' category with no load in the back.

I believe the limiting factor is the load in the recovery. The category has a 2.5g limit in clean configuration and you would exceed Vne in the dive at 2.5g.

Of course it will recover from a spin but probably require full forward stick to be maintained before it does(like the Chippie(not that I've ever had any problem with that)).

That's if you can get it to spin in the first place, which always seems to be the problem with these uninspiring types.

The PA28-161's max g loads are 3.8g for normal and 4.4g for utility, exactly the same as the -140.

And minus 1.4/1.7 IIRC.
There was an AD on the pa28 series several years ago, following a breakup in the US in turbulence, something to do with a modification to the main spar on over 10000hr a/c. That's the only inflight breakup I've heard of, apart from a few that have been involved in spiral dives after entering IMC.
I've done a bit of spinning in pa38's, c152/172, and attempted them in 140's and Airtourers. Closest I could come was a waffly rotation that became a spiral dive. That said, I had a lot more confidence in the structural integrity of the Cherokee over the Tomahawk any day! Probably just a perception thing. The hatchet is a brilliant spin trainer. (Except for the occasional failure to recover situation.) And the 172 is an old lady that prefers to keep a little power on to better stay in the spin. Haven't been game to try anything like this with an aft c/g though. Never will, either.

contacttower118.2 ponders:

Related thread - When management perceives a liability or PR issue, they often take a coward's retreat. :rolleyes: