April 2019

Newsletter- April 2019

Earlier this month I flew the first UK example of the HX11 wing from Grif Italia. This was originally planned as a replacement for the venerable Chaser wing that has dominated international competitions for the last 30 years. Unfortunately the Chaser is no longer in production, and the design team at Grif thought they could offer improvements in handling and efficiency to competition and touring pilots. However, they might have accidentally created something special for the sub-70 market- see below!

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At 11m² (there is a 12m² variant also available), the HX11 is a small wing, but thanks to the lighter trikes and engines available now compared with the early days of the Chaser that translates to a much lower wing loading. This gives the wing a softer ride in turbulence and a much lower sink rate. I was even able to stay airbourne in the early spring thermals- something I’d never even contemplate on my old Chaser!

Flown on the Snake trike (at around 155kg all up weight), hands-off trim speed was around 45mph, with a top speed of 55mph. However, this was flown near the rear hang-point position, and didn’t seem anywhere near the pitch limits of the wing. I’m confident that a further forward hang-point or heavier trike would allow higher cruise speeds.

The efficiency of the wing was such that I had ample power (from a 27Hp C-Max engine) to climb even at full speed. On a heavier trike or faster trim setting more power may be advisable.

Grif HX11 wing as fitted to the Snake nanolight trike.
Grif HX11 wing fitted to the Snake nanolight trike.

The handling was typical of Grif wings- very light in both roll and pitch. This allowed flying in turbulence with only a couple of fingers on the bar. The wing also exhibited very little adverse yaw- which is something the Chaser used to suffer quite badly.

The stall break was reasonably pronounced, and quite often ended up with a wing drop of no more than 30°. In its current guise this is a wing best suited for experienced flexwing pilots.

However (and this is where it gets interesting for the sub-70 market), the stall occurred around 25mph calibrated airspeed. This means it *may* be possible to comply with the 20knot (23mph) stall speed requirement of the sub-70 exemption when flown with the vortex generators installed. The vortex generator option has the effect of reducing the stall speed on the 3DC wing by 3-4mph, as well as changing the stall characteristics to a very benign mush. If the same effect can be realised on the HX11, then we have the potential for a much higher speed wing within this category than has been achieved before.

Grif HX11 top surface
Clean top surface on the HX11 wing.

Understandably, the customer for this wing (a very experienced microlight pilot) was keen to get it home to fit to his existing trike, so I didn’t get much time to play with hang-point adjustment or fitting the vortex generators. A lot more testing needs to be done by myself and Grif before we can be confident this wing complies with the sub-70 category. However, even as an SSDR microlight the HX11 represents a great balance between performance and handling, and would be my choice if I were still competing on the British team.

The HX11 wing weighed in at 29kg, and retains the 190kg MTOW of the nanolight frame it’s based on. This was based on a “no-worse-case” calculation as some of the parts have been beefed up for the HX series, so it’s possible Grif may be able to test to a higher loading in the future.

At £5,520 including VAT this wing comes in at over £1K more than the delightful Grif Zip, so it won’t be for everybody. I’ll be sure to keep you informed of any developments throughout the year, but please contact me if you have any specific questions.

Don’t forget that it’s the Popham Microlight Rally on May 4th & 5th. Please come and say hello! You’ll also have the opportunity to sit in the new “Evo Speed” enclosed cockpit of the Minifox, and see the new tundra tyre concept fitted to one of our Snake demonstrators. We might also have one or two special show offers available, so bring your cheque book!

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