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Other UltralightsUltra light sailplanes

I’ve reported on light sailplanes over the last year in the Oz Report (http://www.davisstraub.com/OZ/Ozv5n174.htm). All the manufacturers that I’ve written articles about showed up at the Aerosports Expo a few weekends ago in Ontario, CA. I got a chance to see the Sparrowhawk, the fuselage of Lighthawk, and the Silent.

There are basically two classes of light sailplanes. Those between 250 and 300 pounds and those at 155 pounds or less, i.e. FAR Part 103 sailplanes. Why 155 pounds or less? No pilot’s license. No FAA certification required. No kits needed – you get the full airplane.

The light sailplanes:

The Silent - http://www.alisport.com/pag_ing/silent.htm

Launched down Monte  Cucco.

The APIS WR - http://www.albastar.si/

Multiple light sailplane world records.

The Ultralight sailplanes:

The Lighthawk - http://www.glidersport.net

The LightHawk Micro-lift Glider will be produced by this original Micro-lift Soaring, technical research and fabrication group. The LightHawk has successfully flown the first flight test program. More information will be posted on the website after Danny Howell has gone over it with the test pilot.

The SparrowHawk - http://www.windward-performance.com/

It flew January 11th. At least one local hang glider pilot has purchased one. Looks like they are ready to put out one a month.

The first question for me is, are these Ultralight sailplanes as strong (g-loading) as the heavy sailplane? At least they don’t have to carry as much weight as the heavy ones due in the rough air.

 

 

Sparrowhawk

I sent a few questions to Greg Cole, principal in the company manufacturing the SparrowHawk, cole@ispllc.net who writes:

The SparrowHawk uses HT grade Divinycell foam. In my opinion this is the best foam available. Please note that this is an aerospace grade of foam and has a very high temperature operational limit and toughness that exceeds all other foams.

The carbon fiber fabric used is special, but is not unique to the SparrowHawk. I have been aware of this fabric for many years through its development cycle. It offers many performance advantages over more conventional fabric. It is true that the SparrowHawk is the first aircraft to fly using this material. Again, this is a high quality aerospace grade material.

We have quoted conservative minimum sink numbers and definitely expect to better them. We have already demonstrated better performance.

By the way we have been to 120 KTS, 9300 FT, and have flights of over 3-hrs duration in the winter. The SparrowHawk climbs and runs very, very well.

The SparrowHawk is very strong. The first aircraft has been tested to limit load before flight testing, and these limit loads exceed those of most sailplanes. Our limits are +5.5 and -4.0 g's with a rough air and maneuvering speed limit of 80 kts. The SparrowHawk is the only light sailplane that I would take into conditions were strong rotors may be encountered.

We have 45 to 45 deg roll response times of 2.7 seconds. This exceeds the roll response of any sailplane I have heard about. Coupled with the high load limits and high-speed capability the SparrowHawk will be as good or better than even the most current generation of modern sailplanes of any size.

You also mention the BRS. This is an option in the SparrowHawk.

http://www.windward-performance.com

Comparing the LightHawk and the SparrowHawk

Why would hang glider pilots be interested in these ultralight sailplanes (or light sailplanes in general)? Because they are the closest thing to hang gliders while still providing vastly superior performance. They are light enough to fly in light conditions and still stay up. We’ll see over the next few years just how they develop and how popular they can become.

LightHawk (http://www.glidersport.net) :

 

Metric

English

Wingspan

15 m

49.2 ft

Wing Area

 

126 sqft

Empty Weight

68 kg

150 lbs

Pilot Weight

45 108 kg

100 240 lbs

Wing loading

10-15 Kg/m^2

2-3.1 lbs/sqft

max glide est.

35:1

35:1

Max glide speed

63 k/h

39 mph

min sink

0.36 m/s

70 fpm

min sink air speed

48 k/h

30 mph

Sink rate at 375 lbs

.46 m/s

90 fpm

Circling diameter

30 meters

100 feet

Stall speed (150 lbs/pilot)

35 k/h

22 mph

Stall speed (225 lbs/pilot)

39 k/h

24 mph

Maneuver speed

80 k/h

60 mph

L/D at Maneuver

26.4

26.4

Red Line speed

161 k/h

100 mph

The LightHawk is designed to be a very light 15-meter sailplane. It is not a scaled down version of a 15-meter sailplane, but a light version of one. The claimed minimum sink rate is only 70 fpm (it looks like this is for a 100 pound pilot), about one half on the minimum sink rate that I measure on my ATOS (not ATOS-C) and I weigh in at 225 with all my equipment. It has a claimed maximum glide ratio of about twice that of an ATOS-C.

The LightHawk is designed to stay up in light conditions and to have a turn radius about that of the Carbon Dragon.

The wing of the LightHawk has three flaperons which account for about 25% of the wing area. While I don’t recall exactly how they work, as I recall inner one operates in a manner to allow one to thermal in a very tight radius.

An anonymous source writes:

The LightHawk is an ultralight sailplane that is optimized for low speed soaring flight. Composite construction is used to provide the necessary strength to meet JAR-22 engineering standards, while weighing only 150 lbs.

The low wing loading and excellent maneuverability will allow pilots to climb in weaker lift than ever before. LightHawk pilots can expect to out climb any other gliding aircraft in the sky, and to get extended flights on even very weak days.

SparrowHawk (http://www.windward-performance.com/):

Wing Span

36.1 FT (11 m)

Wing Area

70.0 FT^2

Length

20.6 FT

Horizontal Span

6.7 FT

Vertical Span

4.5 FT

Aspect Ratio

18.6

Wing Loading

5-6 LBS/FT^2

Load Factors:

Maneuver limit load factors       +5.48g/-4.0g

Critical Speeds:

Maneuvering and Rough Air Speed Limit of 92 mph

Redline at 142 mph

At 350 LBS the minimum sink rate is 123 FPM and the stall speed is 37 mph

Max L/D of 32 is occurs at 52 mph. L/D is 22 at 86 mph.

The SparrowHawk is a scaled down version of a 15-meter sailplane. (Called 13 meters, it appears to be 11 meters.) It has twice the wing loading of the LightHawk and consequently about a 30% higher minimum sink rate (with a 200 to 225 pound pilot). It also has a 50% higher maneuver air speed limit (92 vs. 60 mph). It will fly at a much higher speed between thermals than the LightHawk.

The stall speed is 32 mph with a 200 pound pilot while that of the LightHawk is 24 mph at 225 pound. The Max L/D speed is 52 mph for an L/D of 32:1 while the LightHawk gets Max L/D at a much slower 39 mph at 35:1. I would expect the SparrowHawk to fly between thermal at about 80-85 mph at an L/D above 22:1 and the LightHawk to fly at 50-55 mph at an L/D above 27:1.

Greg Cole writes:

Although the SparrowHawk will be a legal ultralight, it is built to be flown in all the same conditions as existing sailplanes. It will cruise between thermals at speeds much greater than existing light sailplanes with more altitude retention. It will climb exceptionally well with its low sink rate and tight turning radius afforded by its low stall speed and small size

You don’t to have a glider private pilot’s license to fly these sailplanes. They won’t be certified by the FAA.

The SparrowHawk is flying. The LightHawk has a little ways to go.

If you had a chance to look at the proposed FAI/CIVL ultralight specifications in yesterday’s Oz Report (and you are willing to do a few unit conversions), you’ll notice that the LightHawk comes close to the proposed specifications for the Ultralight (or Microlight) class at a wing loading of 10-15 Kg/m^2 (13.6 with 90 kg pilot). The SparrowHawk comes in at 24 to 29 Kg/m^2 (25 with 90 kg pilot) which would put it in the light sailplane class but with ultralight weight.

13.6 Kg/m^2 is near the upper light of the proposed Ultralight sailplane class. Danny Howell (who heads up the LightHawk production team) is asking for up to 18 Kg/m^2.

Break those Carbon Dragons

The other day here at Wallaby Ranch Steve Arndt broke his Carbon Dragon when he didn’t put in the bottom bolts that connected the wing to the fuselage. George Ferris and I were engaged in quite a discussion with him at the time that he was putting the wings on and just as he was about to put the bottom bolts in we talked about how many bolts were needed.

Steve is a very meticulous guy and was obviously very embarrassed that he could make such a mistake. He rolled down the grass field behind the tug and when he got some speed, the wing lifted off, ripping out some bulkhead materials, and rotated over the top of the fuselage. Steve thankfully never got off the ground.

Two Carbon Dragons built and two damaged. I’ve been “involved” in both of incidents that damaged both Carbon Dragons.

Steve hopes to get it repaired soon. Gary Osoba has a standing invite to come down and fly it in Florida and he’d like to come down each month for the Flytec Championship.

Steve is working on a new fuselage that will allow him to include two quarter scale RC motors that will provide ten horse power each. Enough to launch.

LightHawk

An anonymous source writes:

A couple of minor corrections.

You wrote: “The claimed minimum sink rate is only 70 fpm (it looks like this is for a 100 pound pilot).”

Actually that was for the middle of the weight range (170 lbs). At 100 lb pilot weight, the sink rate may be less than 60 fpm. No promises until we measure it, of course.

Also, you mentioned: "a turn radius about that of the Carbon Dragon".

Actually, it should turn quite a bit tighter than a Carbon Dragon due to improvements in the lift distribution when circling. The CD has a single flaperon on each side, which requires a high angle of attack at the inboard tip when circling. To avoid a tip stall and spin, the CD must fly faster than the LightHawk when circling.

(editor’s note: It is my understanding that the turn radius of the Carbon Dragon is 15 meters, the same value indicated for the LightHawk. I may have that wrong.)

The LightHawk uses a segmented flaperon (three per side) so that the tip can be better controlled in low-speed circling flight.

To me, the reported Va (maneuver speed) indicated in the article very conservative. With appropriate flap settings, I think it will be much higher. Perhaps the one in the article was the Va for 20 deg flaps?

Also, the sink rate at 375 lbs should be more like 78 fpm per my calculations. As noted above, they're all paper numbers until we fly and measure the performance.

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