Speed Calculation

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Ryan Smith
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Speed Calculation

Post by Ryan Smith »

Assume the following:

C-145/O-300
Bare 6.00x6 wheels
76x55 propeller
Red paint

Turns into:

O-300D
Sportsman STOL
Micro VGs
76x55 propeller
Wheelpants
Red paint

What happens to speeds?

A recent issue of Cessna Flyer has an "entry level airplanes" article, and the cover shot is a beautiful '52 that's polished with red trim, and has a Sportsman STOL and Micro VGs. Appears to have the stock engine. I'm curious of a few things:

1. Is there a tangible benefit to a flatlander to install magic on the wings and not address the installation of a bigger engine?

2. Is there a speed penalty for either the Micro VGs or Sportsman STOL (or both combined)? I've seen Jim Wildharber rib someone about his airplane being faster with a STOL kit than theirs without.

John Barrett's airplane has a STOL kit, but a bigger engine. I flew it when I was still far from even being a current student pilot, so I'm sure there were a ton of nuances in his airplane that were lost on me at the time. I was farting around a couple of weeks ago when Zenda flew the 170 down to give a few checkrides at my flight school, and took the old girl up for an hour before my first student of the day. Dead calm morning, had the airplane stopped in less than 300 feet without trying too hard. Stock wing, 1305 empty weight. Didn't feel unstable on my approach, but I'm curious of the performance gains for a stock airframe that one doesn't intent to do a lot (read any) real backcountry flying. I'd much rather fly a 180 in the backcountry given my experience with the two.

Please don't lynch me for saying, but I feel Cessna designed a damn good airplane, and one that is very versatile in the stock configuration. I've grown fond of the way the old girl (56D) flies after flying her the last 20 years, and I'm scared to mess up what's there, but I'm really wondering "what if".

I don't consider myself an exceptional pilot, but if I can get the airplane stopped that short without pushing it at all, I'm impressed. It's nothing that will win Valdez, but it's good enough for what I use the airplane for. If it doesn't negatively impact flight performance (handling or speed) and increases safety (which I feel it undoubtedly would), there can't really be a negative. Any thoughts from the collective on this? I'd love a chance to fly a stock airplane with Sportsman and VGs for a feel/comparison someday. I want to be Richard Pulley someday and have an example of every sweet tailwheel model Cessna ever made to suit my mood that day, but until then, I can only dream and wonder.
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pdb
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Re: Speed Calculation

Post by pdb »

Ryan Smith wrote: 1. Is there a tangible benefit to a flatlander to install magic on the wings and not address the installation of a bigger engine?

2. Is there a speed penalty for either the Micro VGs or Sportsman STOL (or both combined)? I've seen Jim Wildharber rib someone about his airplane being faster with a STOL kit than theirs without.
To answer #1, I think the answer is a clear yes as far as VGs go with the understanding that you will not be buying much if any takeoff or climb performance but you will definitely be buying enhanced slow speed safety and handling that will payoff in truly short field operation. (There are some pretty good discussions if you search on this issue that I will not address again here.) I have no personal experience with the Sportsman kit but my belief is that you will also get enhanced slow speed performance and handling and possibly better climb as well if the manufacturer's claims are true. Others who have the Sportsman kit should chime in. Both mods would enhance the performance and safety regardless of the engine on approach at low speeds.

#2 is particularly interesting question. With respect to VGs, the manufacturer claims, and I have experienced, no measurable effect in cruise. As far as the Sportsman kit is concerned, the manufacturer cites other sources that suggest that the glide ratio (L/D) increases from 7/1 for the stock wing to 13/1 with the kit. If this is correct, since the weight has increased only by an insignificant 17lbs or so, the induced drag must decrease considerably. Less drag = faster speed, all other things being equal. I would really like to hear what Sportsman's kit owners report on speed.
Pete Brown
Anchorage, Alaska
N4563C 1953 170B
http://farm3.staticflickr.com/2366/2527 ... 4e43_b.jpg
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GAHorn
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Re: Speed Calculation

Post by GAHorn »

Ryan Smith wrote:...Please don't lynch me for saying, but I feel Cessna designed a damn good airplane, and one that is very versatile in the stock configuration. ....

WHY... would anyone "lynch" you for making the observation that most ALL OF US know and appreciate...but fail to verbalize as well as you did?

One of the very REASONs we love this airplane often goes unstated.... It's a DAMN GOOD AIRPLANE, and one that is very versatile in the stock configuration!

I have gone on record many times unfavorably disposed to VGs and STOL kits on this airplane. Not for the reasons most people think, however.
The reason I feel that way is because after disfiguring the airplane with all that expensive stuff .... you still don't have the best airplane for the job imagined. All you've accomplished is spent a lot of money to make minor "improvement" and detracted from the future originality value of the airplane.

And I thoroughly disagree with use of the words "improved slow-flight safety". (sorry Pete) Here's why: Slow flight safety is 100% in the hands of the pilot. Regardless of the modification-standard of the airframe...if the pilot flys on the lower edge of aircraft performance capabilities in a sloppy-airmanship manner... it will be unsafe. It MAKES NO DIFFERENCE what that stall speed or safe maneuvering speed is. SAFETY is in the hands of the operator and his skill-set in managing the limitations of the aircraft.

(I realize that STOL kits have the capability of reducing flying speeds and modifying control-wheel-feedback/sensory to the pilot... but if he is reckless or sloppy or below-grade in airmanship, it makes no difference with regard to "safety".... He's UN-safe in either airplane. So I do not like it when someone claims that a mechanical configuration-change will make someone a "safer" pilot. The ham-handed drivers with pilot certificates will be just as unsafe in either aircraft. I guarantee that Bruce Fenstermacher can fly a standard 170 safer at really slow speeds than half the owners who read this regardless of whether or not they have a STOL kit or VGs.)

If you are someone who really wants to fly at 42 mph and land in 200' in FarmerJones field because it makes you excited to pretend you're a bush pilot... or if you really do want to land on sandbars in the Yukon... then there are far better airplanes to do that with than a 170 that's been doctored-up and devalued with VGs and STOL kits. IMO. Virtually any standard MAULE will beat a 170 at that game.

Answer #1: No.
Answer #2: Any speed penalty is so small as to be insignificant.

OK. That's my rant. :twisted:
'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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GAHorn
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Re: Speed Calculation

Post by GAHorn »

OK, Arash.... you just proved the point again... Firstly: I did not say that VGs won't change handling. THAT WAS NOT MY point.

If a sloppy pilot learns that VGs will allow him to play around with his ailerons in a full stall .... he will go out and do just that... play around at speeds and maneuvers he decidedly does not understand or have the skill-set to recover when it suddenly flips-over on it's back. The VGs did not "make him safer"... it tantalized him into a flight-regime he has NO BUSINESS playing around with. That is my experience in 47 years as a flight instructor.

Now it's true that a pilot who really wants to operate that slowly and is willing to put in the training to become proficient at it...can certainly take advantage of that improvement. However the average guy with spare change who wants to spend it on his airplane would be far better served to get another rating or get additional training spending that money on a CFI and fuel ... than on gadgets. The "average" guy who gets those VGs actually has no real need for them but will not be able to resist trying to do things he has no business doing in places he never should. I'm talking about the "average guy".... not the professional fishing-guide in Idaho... who has a truly-capable airplane like a 185 on tundra-tires or such...or someone like fishdoc who clearly has a special type of operation and is competent in that special use, not a "wannabe"...

YES. VGs improve handing where most pilots have no need to be handling. Especially Walter Mitty's who wanna believe they're test-pilots for bush-plane builders. Those guys should devote their attention to getting that instrument rating or some aerobatic training or a float-rating, etc. ...something that will really do something for their pilot skills instead of relying on gimmickry that will taunt them into flight regimes with which they have no need and no experience.

Again... just my modest opinion.
'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. ;)
Pdogace
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Re: Speed Calculation

Post by Pdogace »

My 170b has a Horton stall kit, no vg's and to get back to Ryan's question I ask why. So I can land in a very short distance with the stall kit, but I never do. Why you may ask. Because, what good does it do me to be able to land in 200' if I need 6 or 700' to take off. My 170 is limited by its little o 300a engine. So I never worry about landing on a short strip, I just worry about taking off. If the runway is less than 2000' I start asking questions. As to the other talk about safety, I know if I am alone in the plane it will not break on a power off stall. With the wheel full aft and power idle all the plane does is buffet very mildly. Just my thoughts.
Preston
1954 C170B "Sweet Caroline"
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TFA170
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Re: Speed Calculation

Post by TFA170 »

Aryana wrote:Every flight in my 170 I am constantly looking for 150' of space that I can stuff it into if the engine quits. Bonus points if there is a road that will have access so that the wings can be popped off and the plane trailered away.
This.

I have a shorter field I'd like to operate out of. VGs and a Sportsman STOL might help, but not as much as an O360 would...or both. It's not the length of the field so much as the crummy approaches (tall trees). But most of the time, I really just would rather hit the softest thing at the slowest possible speed...both modifications help in the off-field landing scenario. Of course, that assumes you train to use those modifications appropriately.

I train to a lot of odd things though, and consider the turn-back option viable with only a few hundred feet...but I practice it at altitude...and double what I can do there as my minimum altitude where I'd consider it. Both of those mods would help that scenario immensely.
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Bruce Fenstermacher
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Re: Speed Calculation

Post by Bruce Fenstermacher »

To Ryan's question with regards to VGs and a flatlander. Yes there are reasons a flatlander might want to install VGs. I can not comment on leading edge cuffs and realize some of the benefits would be the same. If you installed either and never pushed the envelope otherwise, should you have a power failure or find yourself to slow, you will be in a better position with the mod (either of them) than without. I personally like the VGs because they can be added and removed with little effort and besides paint blemishes leave little behind for the effort. And they work really well at what they do. Increase controllability at slow speed.

To George's point they are likely not going to make an unsafe pilot safe, but they do increase a safety margin at slow speed. Even for the unsafe pilot. Problem with the Unsafe guy is he's going to blow right through the greater safety margin.

BTW having a plane that can float down the runway at slow speed is sometimes not desirable. While I've enjoyed having the extra control as I danced on the rudder, elevator and aileron to get those tires to touch just so nice in a heck of a cross wind. Once the tires touch, one sometimes would like to through out an anchor and keep it on the ground. This can be a little harder if your plane likes to fly.

Any model of 170 is a darn good airplane as it came from the factory. It can be tweaked of course but it is not necessary for most operators under most conditions. I operate my stock A model on a standard prop off a field that is challenging and not much room for error on a good day. It is the kind of field you don't operate at without a briefing how to do it safely before hand. We could improve our room for error with, first a climb prop (which we already own) and next Vg's. We've done neither yet. I'm thinking we might come to our senses and find a better field at 3 times the cost. There's always something to think about isn't there.
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Joe Moilanen
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Re: Speed Calculation

Post by Joe Moilanen »

I put a Sportsmans STOL on my B model last year. I have an 0300D with a 8043 prop. Going in and out of my 650' strip with trees on the approach and departure feels a lot more comfortable now...

Joe
Pdogace
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Re: Speed Calculation

Post by Pdogace »

Aryana, I see your point on emergency landings. I too see a football field or what ever and think I could put it in the slot if I needed too. I guess it depends on where you fly at. Around my area, there are tons of farm fields, airports, and sandy beaches I would look too first. I have lost a engine at night in a single, shut one down on a turbo prop, and had one explode on on a 717. So your point is not lost on me. But if the worst case happens hopefully there is a better choice than a 200' slot to put it in. And if the worst case happens always remember F=M xA. The point being mass is constant and it's best to spread the force over a distance to be able to walk away. My single engine falifure I was able to make it to an airport. For the average GA guy I hope you pick the best option with more room than you would ever think you need so if your short or long your good to walk away. On the west coast your options may be way limited so I get that. I have never flown a stock 170 so all I know is my plane with the Horton stol kit. I don't know if it really make much difference. I would be more than happy to let Ryan fly mine the next time I come to NC and see what the difference is for him. I come home to Lake Norman several times a year so Ryan it's a honest invite if you want to meet up. I have no idea if it helps at cruise. I think, I say this because my prop is a bit of a mystery at this point, I have a a 51 pitch and cruise at 100kts. That's what I plan but it does closer to 105kts above 5000' at 2600 rpm. I run it hard because we are trying to get to our destination as quick as we can with 2 little ones. I have heard that wheel pants add 5 mph but we have 7x6 and no wheel pants. So the answer to Ryan's question would be I am not sure if STOL KITS or VGs add to cruise speed, but wheel pants do and a cruise prop does. The STOL KITS and VGs might help out in the worst case scenario.
Preston
1954 C170B "Sweet Caroline"
Pdogace
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Re: Speed Calculation

Post by Pdogace »

If I was going to puch through trees in rough country, having a little more volocity to sheer my wings might be a better option than dropping straight down 50 feet. No right answer here just good stuff to think about. Luckily our o 300 engines and great. Hitting the trees at 30 and dropping straight down 50' might not be the best option. Plowing throw at 70 and spreading the force over the trees might work better. Depends on the situation. Food for thought.
Preston
1954 C170B "Sweet Caroline"
Pdogace
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Re: Speed Calculation

Post by Pdogace »

The way I read you last post, I assumed you were implying hitting trees at a full stall and hoping for the best. I was just offering another way to approach a really bad situation. Sound like we are both sort of on the same band wagon with the difference being I dont think slower is Always better. This post is about cruise speed increase so I will let it get back to that.
Preston
1954 C170B "Sweet Caroline"
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pdb
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Re: Speed Calculation

Post by pdb »

Aryana wrote: Hitting something at 35 mph vs 70 or 80 can be the difference between walking away and not.
This a big deal. The energy in a crash goes up by the square of the velocity which means that hitting something at 70 will expose you and the plane to 4 times the energy than hitting it at 35. Perhaps more realistically, hitting at 50 vs 40 still exposes you to 1.5 times the energy.

Lower crash energy means less chance of bending and/or breaking your body or bird. Survivability goes way up as speed decreases. VGs give you a much better chance of dropping the crash energy by half and thereby doubling the chances of survival in the event you have to land in someplace really ugly.

BTW, supernice touch down in the video Arash.
Pete Brown
Anchorage, Alaska
N4563C 1953 170B
http://farm3.staticflickr.com/2366/2527 ... 4e43_b.jpg
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Bruce Fenstermacher
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Re: Speed Calculation

Post by Bruce Fenstermacher »

Arash, just saw your picture of the Sierra Nevada mountains. I thought it a picture of the Appalachian Mountains that run through PA and much of the area I fly over all the time. Of course in Pa, it's not the same altitude but the terrain is just as inhospitable to landing aircraft.
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lowNslow
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Re: Speed Calculation

Post by lowNslow »

Bruce Fenstermacher wrote: I thought it a picture of the Appalachian Mountains that run through PA and much of the area I fly over all the time. Of course in Pa, it's not the same altitude but the terrain is just as inhospitable to landing aircraft.
Sorry Bruce, out west we call those Appalachains hills not mountains.
Karl
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Bruce Fenstermacher
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Re: Speed Calculation

Post by Bruce Fenstermacher »

lowNslow wrote:
Bruce Fenstermacher wrote: I thought it a picture of the Appalachian Mountains that run through PA and much of the area I fly over all the time. Of course in Pa, it's not the same altitude but the terrain is just as inhospitable to landing aircraft.
Sorry Bruce, out west we call those Appalachains hills not mountains.
Yes I know Karl. Thing is, a hill in a place you need a runway and there isn't one, will hurt just as bad as a mountain.
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