zodierocket(at)hsfx.ca
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 Posted: Tue Sep 18, 2007 3:28 am Post subject: STOL Landings |
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This is for the Archives, and for the fact that I have been asked several times.
Mark Townsend
Can-Zac Aviation Ltd.
president(at)can-zacaviation.com
www.can-zacaviation.com
[b]Flying the STOL CH 701[/b]
STOL CH 701 – FLAP OPERATIONS
[The following was supplied by M. Stewart of Australia]
Several owners and pilots of the STOL CH 701 aircraft have asked for details on the correct method of effecting a full or partial flap landing with the STOL CH 701. Because the aircraft is principally a STOL aircraft, it does have certain flight characteristics, which are particular to this design. Such design features as its STOL handling, rugged construction and all-metal airframe, large baggage compartment and easy step in – step out access make the CH701 an excellent bush aircraft. The aircraft has a very forgiving and wise "comfort zone", where you can fly without flap or even with partial flap, with the expectation that it will handle "conventionally". This is the nicest zone to fly in and requires little extra skill than the normal or ab-initial pilot would possess.
However, like any airplane, it needs to be understood and true short field handling requires practice, no matter what your flying skills. The airplane can be landed quite safely and without power in all flap settings. What is required for the more exotic maneuvers, I say again, is practice.
First, let us take a look at the aircraft wing. It has a fixed leading edge slat. This produces much higher amounts of lift than a regular wing but the trade off is increased drag.
[img]cid:image001.gif(at)01C7F9C5.437AE6F0[/img]
Next, let us consider the full-length flaperons. Again, much higher lifting potential on full extension, coming down some 35 degrees and in effect have an "air brake" effect on the aircraft.
Although exceptionally strong, the airplane is still a very light design (ie. an Ultralight) and therefore, its kinetic energy is less than a much heavier (general aviation) aircraft. As such, once it picks up extra drag, it either requires more thrust to match or it slows down. This thrust is either with engine power, or by lowering the nose more.
In essence, if the STOL CH 701 is flying "clean" (the nice comfort zone), it flies little different to any other "regular" aircraft of its size. Once flap is selected, the geometry of the aircraft alters and as a consequence, the pilot must modify the handling – albeit slightly.
If the pilot wishes to learn the more exotic STOL handling of the airplane, there are two ways the STOL CH 701 pilot can learn. For simplicity, I will list them.
To begin with, there is no substitute for going two up with either a qualified instructor or STOL CH 701 pilot who is current in handling STOL aircraft in short field techniques with flaps. If you don’t have that good fortune, the following is a guide in building up the required experience in handling the STOL CH 701 with flaps: - Choose a calm air day. Don’t try to practice on gusty or bumpy days. You need to know how your aircraft is handling in calm air, before you take on the rough stuff. STOL aircraft are more sensitive to gusts and bumps, when set up with flap, etc. – that’s why they’re STOL!
- If you are a low time pilot you should initially build up to 20 or 30 hours of "comfort zone" flying. That is to say, don’t use the flap at all. Just get used to the "feel" of the STOL CH 701. If you are a more experienced pilot you will no doubt cut that initial period down dramatically. Even in the flapless condition, you will be able to enjoy very short field handling of the STOL CH 701. Some 701 pilots simply ignore the flaps, as they get all the enjoyment they need with the aircraft flying clean.
- Once you have a feel of the STOL CH 701, take it up to a safe height for upper air work. Bring the airspeed back to under flap extension speed. Apply ½ flap. Then, keeping under the flap extension speed, just fly the airplane around for awhile until you are acquainted with the lower nose attitude and handling -and the need for more engine power.
- Once you are comfortable with the new attitude, try a couple of stalls with the power off. This exercise is performed to reacquaint you with your stall speed. Next try coming in to the stall very slowly. You will notice the aircraft tends to hold its nose up, or even level - and starts to "mush" downwards. Learn to recognize the airspeed just before it starts the mush. That is the airspeed you need to be above on flare once you start the actual landings. Make a note of it and give yourself a few knots above as your minimum - just for extra safety.
- Then, put the aircraft into a glide approach, making a decision to effect a flare at say, 1,500 ft AGL. A VSI is helpful but you should be able to feel rise or fall through your seat.
- Once you get to your designated height, practice with and without power. Imagine flaring the airplane at the exact designated height. Take note of your airspeed. You will notice that the ASI drops off more rapidly with ½ flap, when compared to nil flap for a similar maneuver. You will also notice a steeper nose down attitude is required for ½ flap.
- Having practiced these approaches, start making powered approaches at the runway with ½ flap. Once you are comfortable, gradually reduce power settings until you are using a glide approach. Note the steeper glide angle.
- When commencing with Full Flap, repeat the above steps. You will also notice the very much steeper descent and lower nose attitude – which is how STOL works. Steep in – steep out. It can be a bit disconcerting and many pilots try to hold the nose of the aircraft at the "comfort zone" attitude and therefore lose airspeed and therefore elevator authority in the final stages of approach and as a result may wheelbarrow the aircraft on.
Remember the cardinal rule with STOL – "[b]Anticipate and Practice[/b]!"
Generally speaking, most STOL approaches with flap should be carried out with a degree of power. Unpowered, full flap approaches are achievable but require good pilot handling skills and a reasonable depth perception – principally in knowing when to flare. Airspeed is the critical factor in minimum speed operations when approaching terra firma. Be ready to go around. Full power will usually kick the STOL CH 701 upwards very smartly – getting you away from the ground.
In Summary: - Try to obtain the services of a qualified instructor or suitably experienced STOL CH 701 pilot. Failing that:
- Fly the airplane for 20-30 hours in the 'flapless' condition, unless you are a high time pilot.
- Make your initial flap approaches onto an imaginary airfield 1,000 or so higher than the ground.
- Graduate your power settings, starting with ½ flap and then going to full flap.
- Keep your airspeed up on approach. (I use 2 kts below Vfe)
- Note the much steeper nose down attitude for the two flap settings.
- Timing of the flare is important. Too soon and speed will bleed off.
- If you think you are sinking too much, apply power smartly until sink is arrested.
- [b]Practice![/b][b] Practice! Practice![/b]
[img]cid:image002.jpg(at)01C7F9C5.437AE6F0[/img]
There are nearly 600 STOL CH 701s flying around the world. My information is that there has never been a fatality. They are used in Africa for one-on-one safari: and in South America into jungle strips and mud flats. They fly into lakes wet and frozen, in the Arctic north of America. They hop in and out of tight spots and flap is used as and when needed. Appreciate this little airplane will fly "conventionally" but when you are ready, it will happily do what you ask of it when tight spots and flap is employed. It will fly "conventionally" and happily give you hours of as much exciting and exotic flying as any STOL pilot properly practiced could wish for!
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