Ulm

[Baywatcher]

I tried flexwing and decided it wasn't for me! Am going for an ULM with a high speed cruise. Anyone got views on the Aerotrophy Sting?

[Rod1]

Yes, it is very good but not PFA aproved.

Rod1

[Genghis the Engineer]

Given that baywatcher shows his location as asia, I'd guess that PFA approval isn't high on his list of priorities.


I took a brief look at the TL2000 Sting a couple of years ago (I seem to remember my photo appeared in one of the flying mags doing so, probably Todays Pilot). Although it came to nothing, I still have the notes on my flight which I've pasted below if they're any use. I've weeded out most of the jargon, so hopefully it's reasonably readable. I only flew it for 45 minutes, so please don't take this as being particularly thorough.


Cockpit

The cockpit is easily entered at either side from the wing, the canopy being a single piece item hinged at the front with three catches – one at either side and one at the rear. All were easily reached from either seat. Cockpit layout was conventional, although an interesting item not previously seen in the UK was an engine management display which monitored normal parameters (in a similar manner to the Rotax Skydat) but in a far smaller space. An unusual feature of this was a “Ready” display once warm-up was properly complete, this is an enhancing feature which could usefully be used on any aircraft.Each seat had a central control column, with a joint throttle quadrant and pitch trimmer lever between and in front of the seats. These were easy to use. A push-pull choke knob was in front of the throttle, although this was not used during the sortie. There was no carburettor heater control.Each seat had pedals which were adjustable, albeit by kneeling on the wing and reaching under the instrument panel, a locking pin held in place by an R clip held each pedal. Whilst initially apparently fiddly, this was easy to use and the main criticism would be the risk of dropping the pin or clip – this could be easily rectified by a small retaining lanyard. The assessing pilot has a functional leg length of 1028mm (4th percentile, RAF tables) and was able to reach the pedals adequately, although a low percentile female pilot would probably need either modification to the pedals or a booster cushion. Toe brakes were fitted on the left hand side only.Visibility was excellent, with a full 360° view all around, and the coaming all round low enough to give superb view whilst taxiing.

Note – Limitations The following limitations were given: VF1=140 kph, VF2=120 kph, Vne=300 kph (162 kn). All are IAS values.

Taxiing.
Taxiing could be performed easily, with an estimated turning circle of about 6ft at the aircraft centreline. Visibility, nosewheel steering and efficient differential braking combined to give ground handling characteristics better than the majority of aircraft in this class.

Take-off
Take-off was performed into a 10kn headwind on a short dry grass runway, method was with 1st stage of flap to commence the roll with full back stick, then check half-forward once fully airborne. Aircraft was climbed out at 120 kph IAS (65 kn IAS), which placed the coaming slightly above the visual horizon. Holding the centreline was easy both during the ground roll and initial climb out. Speed control could be maintained adequately within ±10kph IAS.Take-off distance was estimated visually to be about 300m to 50ft, initial climb rate was not assessed specifically, but was good.

Handling tests – general
A series of handling tests were carried out. These were carried out in the cruise configuration, in light to nil turbulence, at nominal conditions of 2,300 ft QFE, 180 kph IAS (97 kn), 4,600 rpm (0.3 bar fuel pressure) which was power to sustain level flight. These various handling tests are detailed below:-

Pitch Stability was extremely shallow, although a gradient could be felt it was very shallow. Further indication of this was given by assessment of the trim speed band, which was ±30 kph IAS (120 to 180 kph IAS). The shallow apparent longitudinal static stability, particularly as evidenced by the very wide trim speed band, is unsatisfactory and should be rectified (highly desirable).

Longitudinal Dynamic Stability (short period and phugoid) were evaluated using a pitch doublet followed by control release, and by accelerating the aircraft by 15 kph IAS and then releasing the control. In both cases, longitudinal dynamic stability was deadbeat, which was satisfactory.

Manoeuvre Stability Manoeuvre stability was assessed by flying steep (approx 2g) level turns. Back-stick pressure was about 1 daN. This indicates that at limit normal acceleration of 4g, the stick force is likely to be around 7 lb which is insufficient for compliance with (UK certification rules) which requires a force of at-least 15 lb.Lack of sufficient manoeuvre stability is UNACCEPTABLE and will require rectification.

Static Lateral and Directional Stability Static Lat-Dir was assessed by carrying out steady heading sideslips to full rudder input to both left and right. With left rudder, about 1” of right stick and very little stick force was needed to hold a steady heading, on release of the controls, the aircraft came to straight flight within about 2 seconds indicating adequate lateral and directional static stability. Sideslip as estimated by the compass was 15°.The same test to the right gave similar handling except than lateral stick input was about 1½” and sideslip was about 25°.Overall lateral and directional static stability were satisfactory, although the characteristics are symptomatic probably of fairly low lateral stability and high aileron power. This combination should be discussed in operating data since this does tend to make the aircraft fairly “lively” something that new pilots to the type should be made aware of.

Trim change with services Trim change with power and flap selection was evaluated. Selecting 1st (take-off) or 2nd (landing) stage of flaps gave very only a slight but progressive nose-down pitching motion, controllable with only a very small back-pressure on the stick. Trim change with power was more noticeable, as power was increased the nose pitched up requiring a firm push forwards on the control column, equating to a stick force of about 4daN from idle to full power. This could be trimmed out easily using the pitch trimmer. There was no discernable change in lateral or directional trim with power selection.Trim change with power and flaps were predictable, trimmable and well within normally acceptable limits, this was satisfactory.

Stalling Stalling characteristics were assessed at about 2000 ft.

The wings level idle stall was assessed in config CR using a deceleration rate of about 2kph IAS per second at about 2,000 ft. Stall warning was afforded initially by a clearly more nose-up pitch attitude than the level or climbing attitudes, athough not by significant rear movement of force on the stick. Moderate airframe buffet was experienced at 90 kph IAS (48 kn IAS) and the stall was marked by a gentle pitch break without half back-stick at around 80 kph IAS (43 kn IAS).

The wings level idle stall was also assessed in config L using a deceleration rate of about 2 kph/s at about 2000 ft. Stall warning was again afforded by the nose-up pitch attitude, but there was no buffet. The stall was marked by a 25° left wing drop but no pitch break at about 85 kph IAS (46 kn IAS).The landing configuration stall gives rise to significant concern. Firstly if the ASI is reasonably accurate, the aircraft does not comply with the requirement that Vso should not be more than 35 kn CAS. In order to reduce technical risk it is ESSENTIAL that further investigation of the stall is carried out on an aircraft which has had the ASI calibrated, so as to determine whether the aircraft meets the UK microlight definition with respect to stalling speed.Also, 25° wing drop at the stall is non-compliant with (UK standards) which do not permit more than 20°. This gives mild cause for concern, since experience on other aircraft has been that fixes for weak longitudinal stability (see above) usually tend to reduce wing drop at the stall. Nonetheless, it should be noted that wing drop at the stall may require improvement.

The aircraft would also be improved if there was some form of natural or artificial stall warning apart from pitch attitude in the landing configuration, since the lack of stall warning combined with significant wing drop at the stall, could lead an inexperienced pilot to lose control on final approach. Also it was noted that the flap limiting speeds of 120 and 140 kph were less than 2 x the full flap stalling speed. If, after the above investigations, this in confirmed to be the case when considering calibrated airspeed (CAS) this will need rectification.

The stall was also investigated in idle power 30° banked turns to both left and right, with power at idle, in config CR, decelerating at about 2 kph/s flying at about 2000 ft. From a right hand turn, the aircraft stalled at about 100 kph IAS (54 kn) with the stall being marked by the aircraft rolling wings level. From a left hand turn the aircraft stalled at about 90 kph IAS (49 kn) with the stall being marked by the aircraft rolling to about 20° right. Stalling characteristics in turning flight were satisfactory.

Approach and Landing An approach and landing were flown with 2nd stage (landing) flap selected using an approach speed of the recommended 120 kph. Handling during the approach was sluggish, particularly in roll, as is common with high speed aeroplanes being flown at low speed on a flapped approach. Lateral and directional control during the approach were satisfactory. The use of flaps clearly reduced the sink rate, such that apart from a fairly nose-up attitude, the approach angle would be familiar to most microlight pilots, which was satisfactory. However, the flap limiting speed of 120 kph is co-incident with the recommended approach speed, which, particularly combined with the shallow pitch stability made it impossible not to exceed the flap limiting speed on the approach. As has already been discussed with respect to stalling, the flap limiting speed is too low, and needs to be increased (ESSENTIAL). The actual landing itself was uneventful, although the lack of pitch stability led to a slight tendency to balloon. Stopping distance was short, with the aid of brakes and the aircraft held the centreline very well even whilst moderate braking pressure was applied.


Summary of Conclusions

Noting that this was only a short assessment of the aircraft, the TL-2000 Sting was a thoroughly enjoyable aeroplane and showed good potential for UK approval in the microlight category. However certain areas gave rise to concern, and these should be investigated before further work. These were (in descending order of importance): Stalling Speed in the landing configuration, Apparent Longitudinal Static Stability, Manoeuvre Stability.

(The last two are almost certainly connected, my best guess would be that the tail is too small!).

G

[Rod1]

That is some flight test!

I flew one about two years ago. I had flown all the similar group A and D machines I could find. The Sting came top! According to my notes the perspective importers were going for group A with a MTOW of 550kg. I abandoned my interest as further investigation lead me to believe it was unlikely to get PFA approval, which turned out to be the case. I ended up with an MCR01 Club, MTOW 490kg, which was the closest I could find. Did you do a flight test on one of those?

Rod1

[Genghis the Engineer]

No, I've not yet had a chance to fly a Ban-Bi. I have been promised a go, but need to get myself in the right place at the right time.

G

[Baywatcher]

Genghis the Engineer

Thanks so much for your detailed reply and air test report. I will hang fire! My address is Asia where I work but I live in France and am looking for the fastest microlight available!

Many thanks

Baywatcher

[Fly Stimulator]

Baywatcher,

Since you're in France you should be able to find the Avril edition of "Aviation et Pilote."

There's an interesting article in there entitled "Dynaéro à Darois : quell gâchis!" on what seems to be a fairly serious breakdown in relations between Dynaéro and some of its customers over faults in the aircraft and the company's response to them.


On another level it's interesting to see a magazine write a hard-hitting article about the shortcomings of a local constructor. I've never seem anything similar in a mainstream UK flying magazine.

[Baywatcher]

Rod1

How have you found your MCR01? I have arranged a test flight in the MCR 4S in a couple of weeks time. Sounds good on paper!:O

[BEagle]

Perhaps one benefit to come from EASA will be that any aircraft certificated for use in any JAA member state (or whatever that term becomes) shall be acceptable for use in any other JAA member state without any further certification being required?

If not, why not?? It should apply from microlights to the A380!

But maybe that's as likely as the PFA stopping the use of the outdated and meaningless term 'Group A'.

[bar shaker]

EASA have (thankfully) delegated the governance of permit aircraft and microlights to the relative national bodies.

[Rod1]

Baywatcher

I am about 2/3 of the way into the build. The UK agent is quite good and the kit has been very good with two minor exceptions. The MCR 4S does look very good, but again is not PFA approved.

Rod1

[Genghis the Engineer]

Beagle, 'tis all about political reality.

Gliders are regulated in France and Germany, who seem to have the casting vote these days on things European - so they decided to hell with what happens to the Brits, we'll regulate them at a European level.

Microlights on the other hand, are formally regulated only in the UK and Germany and not at-all in France. So, the French gave themselves the casting vote and decided that EASA should leave them alone - whilst the large UK and German microlight industries would actually cope with that quite well and might use their greater familiarity with a regulated environmnt to swamp - err, the much less technically competent French industry.

Looks like a French world take-over the more you look at it.

G

[Baywatcher]

Rod1

If it doesn't have PFA approval, does it mean it can't fly in UK airspace?

Presumable the 01 that you are building is approved?

[Rod1]

The tri gear MCR01 VLA, Club and ULM are all approved. You could operate an MCR04 on a French reg, in UK airspace, for about 30 days a year. The CAA can extend this under special circumstances.

My idea of perfect European harmony would be to allow all current rules to stand but to allow any approved aircraft to operate in any European market. We would have 3 times the choice at substantially reduced cost!

Rod1

[bar shaker]

Rod

That's the problem (for us) with the French stuff, it isn't approved by anyone.

Despite this, they produce some of the most stylish and well built microlights in the world.