Slow flight

Slow flight

<HTML>Does anyone have STOL modifications installed on a 172M ( has Cessna's later style leading edge) and have genuine performance improvement numbers? Trying to get slower for aerial photos. It seems that by using lots of flaps and power you can get the indicated airspeed a lot lower, but the groundspeed doesn't drop much........

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Jim</HTML>

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Re: Slow flight

<HTML>Jim
I live in Cheyenne, Wy. 6100' and operate off of a 1900' grass strip. I used to own a nice 1960 172 but often due to density altitude in the summer I could not get off safely with much fuel on board. I put a Horton STOL kit on it and although it did not completely solve the problem it did allow me to get off when before I would not have been able to. I can't tell you how much slower for it was below what my airspeed indicator would register. Also on landing where before I had plenty of elevator for full stall landings with the STOL I would be enough slower that I would have to pull the yolk all the way back against the stop. Cruise I could see no difference one way or the other. One other thing airelon (how do you spell it) roll control was improved at slow speeds

Larry J</HTML>

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Re: Slow flight

<HTML>One problem with determining "real numbers" for STOL (and other) airframe modifications is a complete lack of properly calibrated flight-test instrumentation and flight-test procedures.  This may seem like a silly thing, but it really is important.  An example is, although some STOL kits claime to significantly reduce stall speed, it's virtually impossible to confirm it due to the standard location of aircraft pitot tubes.  With all the drag/lift devices deployed the angle of attack is such that the standard pitot tube is incapable of receiving undisturbed airflow which doesn't impinge upon the tube's mouth and walls with excessive turbulence.   The result is that the aircraft's (also-standard) airspeed indicator is unable to detect and display meaningful differences in data.  In other words, most owner's impressions of their "before and after" experiences are heavily influenced by what I call a "feelgood factor".  If a lot of money is spent on aftermarket mods that make noticeable differences in perceived angles of attack, then the owner usually has a high "feelgood factor", regardless of whether or not anything other than airframe attitude is affected.  It LOOKS slower, so it must BE slower, right?
Aerial photography rarely requires slower airspeeds.  If you're having difficulty getting clear shots, slower flight is not likely to improve the situation.  In fact it sometimes worsens it due to the aircraft's longer exposure to up and down-drafts which complicate accurate altitude-hold.  Many times engine heat and exhaust heat are also the cause of blurred images.  A re-direct of those exhausts sometimes is more helpful than slower flight.  Most professionally equipped photo-planes have accomodations to deal with such problems, and are included in approved mods for the aircraft.</HTML>

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Re: Slow flight

<HTML>Wish to note a slight disagreement with Mr Horn's comment that slow airspeeds don't help air to mud picture taking much. Air to Air, I'd probably agree with him. I find that the slower speeds allowed with the greater control and stability that my Superdroop tips and gap seals afford greatly increased picture quality. Same with STOL kits like Bush or Horton.You have less air flow buffeting you, the camara, and the lens with the windows wide open and the you frequently don't have to bank as much or as hard or take as many G's in a turn. You have more time to get the shot or more shots (if not in severe turbulence.) This is true with a manual or an autofocus or a digital. Since this has digressed from STOL kits to Aerial photography, I also have my windows openned up 90 degrees by removing the window angle limiting bracket arm and securing the window to the bottom of the wing through the use of a duct tape padded 31 inch trucker's bungie cord strapped between the fresh air intake slot and the inboard flap slot. Doesn't interfer with the flap actuation in any of the high wings Cessas like the 150, 152, 170, 172, 175, 180, 182, 182RG, 205, 206, but obviously check this out for yourself on the ground in each airplane before you fly. Haven't tried a 177, 207, 208, or 210 yet. Don't forget and try to open the door with the window strapped up like this. Don't forget to install clear urethane furniture bumper pads to the bottom edge of the window to prevent scratching the paint on the window and the bottom of the wing. Don't loose those little bearings in the window bracket when you unscrew the limiting bracket arm as they are rather pricey to replace. While airflow will hold the window up MOST of the time, it won't do it 100% of the time, and Mr. Murphy says that the one moment it won't is the one that has you concentrating on what you see through the extra good 28 - 300 mm telephoto that you don't want to replace, while the PIC cuts your own wake in a steep banked 360. If you want to fly closer to "the edge" and get the most out of your STOL devices with greater safety, install, calibrate properly, and learn to use a Huntington Lift Reserve Indicator and a GPS. Most factory ASI's don't go low enough to reflect the actual speeds, even if the pitot system was properly placed for those AOA's and they don't react fast enough at those speeds. You don't really care how fast you are going, but how much lift you have left and where the "edge" is. We frequently fly entire search missions in slow flight "search mode" and the greater control afforded by STOL devices for crank and bank flying is worth every penny. A better quality lens will give you more light to get "that shot". So will shooting between 10AM and 2PM for most shots on sunny days unless your subject is hidden by canopy at that time of day. Never had an exhaust plume affect any of my shots yet, but have heard of this. Turning (rotating) the exhaust stack is said to be easily approved via a form 337, and not very difficult. I have heard that this can affect the engine temperatures. I have flown with both the Bush and the Horton STOL kits. They are both quality kits that do dramatically affect the low speed performance of high wing Cessnas. Check your speeds with a GPS if you want numbers and then carefully explore the new envelope and what it can do. Remember you can take pictures OR fly the plane safely, but not both. Let someone else do one of the jobs correctly while you do yours safely.</HTML>

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