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Re: New SSDR regulation

Posted: Wed May 28, 2014 5:52 pm
by Basil
At last! Now our SD1 kit can fly when we finish it instead of being an expensive ornament. ... 014091.pdf

Re: New SSDR regulation

Posted: Fri May 30, 2014 9:31 am
by John Riley
Well done Basil. After numerous emails to various people at the CAA, you post was the first I heard of this.
At last we have it, too late for me to go to Sywell but the exemption is exactly what we wanted and expected.

Re: New SSDR regulation

Posted: Sat May 31, 2014 2:14 pm
by cardiffrob
Sorry to be a bit dim, but...
...Can a Fred, stalls @ 40 mph (according to spec sheet), weighing 354 MTOW, built and flown in the 1980s now be eligible for SSDR? I have a photo of it showing 28kts at some point whilst still airborne so I was also wondering how one converts from indicated to calibrated?

What would be the next 'move'?


Rob. (Dimmed by some fantastic pain medication this week!)

Re: New SSDR regulation

Posted: Mon Jun 02, 2014 1:04 pm
by Ian Melville
Sorry Rob,
Too heavy. 300Kg is the max without a chute. Stall may be OK, but it is the CAS, not IAS that should be less than 35Kts. Not sure how calibration is done, but I suspect there will be calibration flights with test kit (if required to prove it complies).

Could a FRED go on a diet, and use a lighter engine? Call it the FREDlite and set a MAUW of 300Kg

Re: New SSDR regulation

Posted: Mon Jun 02, 2014 1:14 pm
by cardiffrob
300 kg for a single seat landplane (or 390 kg for a single seat landplane of
which 51% was built by an amateur, or non-profit making association of
amateurs, for their own purposes and without any commercial objective, in
respect of which a Permit to Fly issued by the CAA was in force prior to
1 January 2003)....

Doesn't it come under the 390kg section, Ian?

Re: New SSDR regulation

Posted: Mon Jun 02, 2014 1:19 pm
by Ian Melville
Good point Rob. If your permit was first issued before 1st Jan 2003. I thought yours was yet to fly? or are you doing a rebuild?

Re: New SSDR regulation

Posted: Mon Jun 02, 2014 3:11 pm
by cardiffrob
Last permit renewal flight in 2003 ended up in a field full of hay bales. Scratch one engine and one undercarriage leg!

If The FRED was permitted to 'go SSDR' then I assume I could fly it quite soon but it might be that the regs would require it to be finished to 'LAA spec' before it can be test flown to prove the stall speed is within SSDR spec, if that makes sense.

The majority of work remaining is paperwork which, whilst not being an impossible task, is something I'd rather avoid if it wasn't necessary. All the rebuild was done to LAA spec but I also played about with a silencer system that was fantastically quiet but would require more paperwork. Avoiding paperwork is partly what SSDR is all about, after all. :D ... 2.mp4.html

The CAA seem quite happy with the calcs from the original design spec but suggested that I check in with Turweston as well. The phones seem to still be unserviceable at LAA HQ.

Re: New SSDR regulation

Posted: Wed Jun 04, 2014 5:41 pm
by cardiffrob
I've just been informed that changing to SSDR is not possible unless the aircraft was previously within the Microlight category and that if it was under the LAA umbrella then it cannot move to SSDR. That's scuppered my plan, then.

Time to close the workshop door again. :(

Re: New SSDR regulation

Posted: Sat Jun 07, 2014 12:57 pm
by John Riley
As far as I understand it, any single seat aeroplane that conforms to the criteria can be deregulated.
When the ANO is updated next year all single seaters that conform to the criteria will be forced to go SSDR.
The MTOW of 300kgs is declared, so if your 354kgs is made up of 90kg pilot and 10gals fuel, and baggage, then it may be possible with less fuel, no baggage and a slim pilot, to take off at 300kgs.
The stall speed is a bit more tricky, anyone got a good way of getting a calibrated stall speed.

Re: New SSDR regulation

Posted: Mon Jun 09, 2014 9:56 am
by cardiffrob
John. There are some grandfather rights for aircraft up to 390kg MTOW so long as they were homebuilt (etc etc) so mine would be 'in' on that score but the stall speed is an issue that the CAA are already looking into. Difficult to prove until the aircraft has flown so there may be need of some sort of alleviation for a test flight to prove 35kt compliance?

Anyway, the best 'calculation' for airspeed is to find the wing profile for an 'infinite' wing that has no tip vortices, a theoretical figure, and then take the maximum coefficient of lift (2.25 for the Gottingen 535 profile on the FRED using a Reynolds number of about 1.5 million), divide it by the aspect ratio factor (AR/AR+2) to get an allowance for the lack of infinite wingspan and then plumb the numbers into the LAA calculator.... ... lator.xlsx

This figure then needs a good fudging for the CofG effect (aft= lower stall speed) and any performance decrement due to manufacturing etc.

This is the best info I've found, so far.

(Usual disclaimer applies since I'm new to all this!)

Re: New SSDR regulation

Posted: Mon Jun 09, 2014 10:10 am
by cardiffrob ... stics.html
Profile for Gottingen 535.

From Google/Wiki...At sea level and at 15 °C, air has a density of approximately 1.225 kg/m3 (0.001225 g/cm3, 0.0023769 slugs/ft3) according to ISA (International Standard Atmosphere).

Reynolds number...

Re: New SSDR regulation

Posted: Tue Jun 10, 2014 1:16 pm
by John Riley
Hi Rob, Thanks for the info. I am aware of the 390kg group of aeroplanes. As this was the old weight limit before they increased it for microlights upto 450kg currently, I thought you may not be eligible to use those rules. I hope it works out for you.
I was thinking of the practical ways of calibrating the airspeed. I was going to fly in three different directions in fairly calm conditions and note the GPS ground speed against the ASI. In theory it should work even in a 15kt wind, but less easy to maintain a steady airspeed.
I would do this at varying speeds, but mainly at just above the stall. My aeroplane should stall at about 28kts at MAUW.
Exciting times, takes me back to flying in the eighties.