170A with the Sportsman STOL Kit?

How to keep the Cessna 170 flying and airworthy.

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GAHorn
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Re: 170A with the Sportsman STOL Kit?

Post by GAHorn »

This post may be viewed as “contradictory”... but please do not do so. That is NOT my intention.

Nor is it my intent to bring any denigration or disparity to anyone’s airplane or person. My intent in the following comment is solely for contemplation and consideration when selecting and/or modifying an airplane
.

Whenever modifying (or considering for purchase a highly-modified airplane) I believe it wise to keep in mind that just because a modification is “approved”... does not make it worthwhile, valuable, or safe even.

In this discussion, it was apparently implied that the STC holder didn’t think it “profitable” to go thru the certification process of their mod to the A-model.

While that may be true, the conclusion one might “leap to” is that there’s no real reason their STOL mod is really any different on an A-model than it is on the B-model (which they clearly DID consider it to be profitable.).

The questions I believe which SHOULD be asked are:
1- Is the STC holder expecting end-users to accept that their only restriction to “profitability” is the smaller number of A-models to B-models..???

<OR>

Is the potential ADDED EXPENSE of getting their mod “Approved” by Certification Authorities the ACTUAL reason for less profit in that model?

2- Is the mod AS SAFE as it should or could be in that skipped A-model? (And does that also apply to the straight 170?

3- How will the mod affect my investment-value? Will my initial belief that a “mod” equates to “improvement” an Actual Fact? Or is it only Perceived?

If I were in the market for an all-metal 170, I would (and DID) add a slight value to the B-model MOSTLY because of it’s minor improvement in performance over the A-model with regard to field-length,... the direct result of it’s larger flaps.
The other reasons I considered the B-model in more favorable light was because it was the direct-ancestor of the hugely popular/numerous follow-on model, the C-172. This gives the B-model (especially the ‘53s and later) more commonality with that 172, and that equates to PARTS AVAILABILITY.

I believe it’s easy to recognize that the 170 airplanes were evolutionary models to the world’s most-numerous/popular airplane, the C-172 series.

I view earlier versions of the 170B to also be great airplanes that share many of the same wonderful/popular characteristics.

But WHY would the STOL/STC holder skip over what most people would consider a practical (if not virtual) TWIN to the B-model?

I suggest it’s because there is an oft-overlooked feature that not many recognize: The TAIL feathers!

The B-model required significant design change to it’s tail, especially the elevators, because of significant handling characteristic changes resulting from those large flaps. This has been cussed/discussed many times with regard to WARNings against slipping the B-model (and 172s) with full flaps deployed.

The STOL modification falls DIRECTLY into the regime of flight where full flaps are usually deployed in landing configuration.
The change in the leading edge of the wing results in a change in Center-of-Lift (C/L) during that portion of flight where the STOL features are most-utilized/most-influential. This leads to the question which will be asked of aerodynamicists: How does the change in wing-characteristics affect elevator effectivity and elevator stall-margins?

I suspect that experienced test pilots and aerodynamicists would require more extensive flight testing of the A-model than the expected sales of that STOL STC would support with regard to “profitability”.... and perhaps, Safety.

I was never an engineering test pilot... only a “production test” pilot... which is mostly a quality-control task, not a certification task.
But this STOL STC not having passed the scrutiny of a full flight-handling-test would concern me if I was considering purchase of airframe mods that have only had a “field approval” by a group of maintenance inspectors.

Just my thoughts. YMMV
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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n2582d
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Re: 170A with the Sportsman STOL Kit?

Post by n2582d »

gahorn wrote: ... But this STOL STC not having passed the scrutiny of a full flight-handling-test would concern me if I was considering purchase of airframe mods that have only had a “field approval” by a group of maintenance inspectors.
In addition to what is described below by a DER test pilot what else would be included to qualify as a “full flight-handling-test”?
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Gary
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GAHorn
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Re: 170A with the Sportsman STOL Kit?

Post by GAHorn »

n2582d wrote:
gahorn wrote: ... But this STOL STC not having passed the scrutiny of a full flight-handling-test would concern me if I was considering purchase of airframe mods that have only had a “field approval” by a group of maintenance inspectors.
In addition to what is described below by a DER test pilot what else would be included to qualify as a “full flight-handling-test”?...
As I stated earlier, I was not disparaging this airplane or any owner.

My post was to provoke thoughts and considerations when making purchasing/modification decisions. Especially when “field approvals” by “maintenance inspectors” are offered for flight-characteristic questions.

The available information in the thread (up to the point of my post) only offered “maintenance inspectors” scrutiny of the mod.... And that was the focus of my comments.... and if full flight testing by qualified engineering test pilots was conducted.... that would go a long way toward the decision-making process about those matters. (At least for myself.)

One still wonders why, in the face of the attachment submitted, what further obstacles the STC holder found troublesome or “unprofitable.”
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
hilltop170
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Re: 170A with the Sportsman STOL Kit?

Post by hilltop170 »

Gary
If you have the rest of the report or even any more of it, would you please post what you have and share it with the rest of us? Or divulge your source so others can look up the additional info?
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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DaveF
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Re: 170A with the Sportsman STOL Kit?

Post by DaveF »

Item 146 from the library has the names of the FAA DER test pilot and the IA who did the 337. If you can contact them you might be able to get the flight test report.

The site is still malfunctioning for me, but I've downloaded 146 and I can email it to you if you need it. It has the 337 and a letter describing the tests performed, but not the actual test flight report.
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n2582d
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Re: 170A with the Sportsman STOL Kit?

Post by n2582d »

As Dave said, see item 146.

We all owe Bruce a beer for the work he went to organizing, scanning, and placing online all those 337 forms. I can't imagine how much time that must have taken. Thanks Bruce, it's much appreciated!
Gary
hilltop170
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Re: 170A with the Sportsman STOL Kit?

Post by hilltop170 »

Thanks! Dave and Gary, and especially Bruce!
Last edited by hilltop170 on Fri Apr 03, 2020 5:49 am, edited 1 time in total.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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c170b53
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Re: 170A with the Sportsman STOL Kit?

Post by c170b53 »

With all these owed enticements (and I’m certainly on the hook for a few) let’s hope we can all get together soon. Thanks gentlemen
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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Bhbackcountry
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Re: 170A with the Sportsman STOL Kit?

Post by Bhbackcountry »

Thanks for all of the info guys! The seller is going to work on getting her approved before the sale.

Will from Stene Aviation sent me the 54 page flight test from #146. He asked that I not post it online but said I could send it to people who are interested. My email is below and I’d be happy to forward it on.

Barstow18(at)hotmail.com
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n2582d
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Re: 170A with the Sportsman STOL Kit?

Post by n2582d »

Does he have any intention of eventually adding the 170A to the AML for the Sportsman STOL kit?
Gary
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Patrick Phillips
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Re: 170A with the Sportsman STOL Kit?

Post by Patrick Phillips »

Does anyone sell a Leading edge cuff approved for the 170A ?
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n2582d
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Re: 170A with the Sportsman STOL Kit?

Post by n2582d »

This thread has your answer.
Gary
KFS1998
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Re: 170A with the Sportsman STOL Kit?

Post by KFS1998 »

Email sent - Bhbackcountry
Future C170 Owner
Miami, FL ( TMB )
TIC170A - 10697
ATP / CFI - Airplane / Glider
FAASTEAM Lead Representative
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