I’m pleased to report some material that might help in the quest suggested by Laurie to research the possibility of modifying the aero restrictions.
First, the original Austrian Type Certificate (23 July 1984) noted as its last sentence: Suitable for cloud flying and simple aerobatics according to the flight manual. We further inquired with Wolf Hoffmann on the subject, and have learned the following: Simple aerobatics mean the following maneuvers: inside loop, hammerhead turn, lazy eight and intentional spin. What motivated SB12 was that during a demo flight which included a spin with several turns, the aircraft needed “more than the usual benign and easy ½ turn” for recovery, and it was found that actually the rearmost flight cg position had been exceeded (one pilot, heavy baggage). The additional tests referred to in the SB indeed were carried out, and showed that the aircraft may take more turns to recover and enter a more flat attitude (esp after 5 turns) if the cg is in an extremely rearward position. (In Kershner’s The Basic Aerobatic Manual he says: “Don’t ever spin any airplane with people or luggage in the back. The developed spin with a rearward c.g. is normally flatter, and the controls may be ineffective for recovery.”) But the reason the aero maneuvers were prohibited was not so much that, as another requirement “the authorities came up with”: the need to demonstrate that the airbrakes would be effective to prevent exceeding VNe in a dive following any attitude resulting from a failed aerobatic maneuver. The manufacturer determined that compliance could not be easily shown and instead issued the SB. Cheers, Kristin Sent from Windows Mail From: [email protected] Sent: Monday, June 27, 2016 8:18 PM To: [email protected] Hi All, I've been reading this thread with interest. In Oz we are required to undergo annual spin checks as part of the Annual Flight Review. For a club like ours only operating the Dimona its inconvenient to have to arrange for access to a conventional glider approved for spinning for our members through another club. The upside is that we get to fly aerotow again and remain reasonably current when we probably wouldn't bother otherwise and also we get reminded of what gliding is all about. Not that gliding engine off isn't the major component of nearly all of our flights including landings, but a reminder of what modern gliders are actually capable of. Over the last couple of years our AFRs have been in a beautiful example of an IS28 just a couple of days before its 30 year retirement (yes not modern but still a better glider than the H36) and in a DG1000. I have to say though that other than the pilot being checked demonstrating their recognition of fairly generic spin onset symptoms and then the standard recovery technique, I'm not so sure about how much value there is for us in spinning a DG1000. It would be far better to be assessed in spin entry and recovery in our Dimona. I assume that this would be the case for almost all Dimona operators in this country at least. Spin checking here involves the three stages of spin prevention, incipient spin recovery and full spin recovery. I regularly investigate incipient spin recovery in GYT and as Nigel says the aircraft's behavior is quite benign, however this has been mainly engine off. I have attached a link to GFA (Gliding Federation of Australia) Operations Advice Notice 02/2012 Annual Flight Reviews. Here is an extract from the section on spinning... For private owners, it is entirely appropriate to take a look at their glider's Flight Manual and discuss the stall / spin characteristics of their machine. Many high performance gliders are not certified for intentional spinning but this does not mean they won't spin! The limitation is usually a consequence of the likelihood of exceeding the glider's VNE in the spin recovery should you get in one. This just wouldn't apply to the H36. Can the engineers advise of whether there is any value in exploring the background for the limitation being imposed and investigating the possibility of the restriction being lifted? I guess this is what Kristin would have in mind. As an aside Kristin, and with no disrespect intended for the skills of your aerobatic friend whatsover, there have been many instances of experienced power aerobatic pilots getting into major strife trying our their aerobatic skills in gliders. Not so long ago here a highly experienced military fighter pilot attempted a rolling maneuver with near catastrophic consequences. As with the prowess of highly experienced power pilots (especial CPLs) often not readily transferring to gliding without considerable conversion training, aerobatics can be the same. Laurie From: "[email protected]" <[email protected]> To: "[email protected]" <[email protected]> Sent: Tuesday, 28 June 2016, 8:57 Subject: Re: [DOG mailing list] Spins Thanks very much for your help, guys. Nige, the aero restrictions on SB 12 came in earlier (Jan 1985). The wing failure from a July 1986 accident in Germany indeed was the result of acc to the investigation high g loading - at high angles of attack. Wolf Hoffmann further said to Tom awhile back commenting on this that the LBA wanted them to “do something” even if no structural imperfection was found, thus the SB 19 winglatch kit. We got the original accident summary from the BFU database, it doesn't say much, but it does say this: Accident in Walchensee on 29.07.1986 Aircraft wing related event (ATA Code:5700) , during Cruise. {Occurrence} Fuselage main bulkheads (ATA Code:5312) Wing attachment fitting (ATA Code:5740) Weather conditions VMC Aircraft SN 36115 D-KESL Aircraft total time 820 Hours *flying club crew experience This Aircraft type 17 Hour(s) All types 1198 Hour(s) Events: primary break of the right wing in the flight (SE) - cruising (D1) |_ FUSELAGE/BULKHEADS (70BA) |_ Not sufficiently firm/solid (88H4) |_ WINGS/WING ATTACHMENT FITTINGS, BOLTS (70AC) |_ Not sufficiently firm/solid (88H4) Sent from Windows Mail From: [email protected] Sent: Saturday, June 25, 2016 10:41 AM To: [email protected] Yep. I have had it go in unintentionally a couple of times while soaring in thermal conditions. A good gust brought it on both times. It is quite benign and relaxing back stick is enough to get a quick recovery from the start of an incipient. I have deliberately done it once to see what it is like although didn’t let it fully develop. Again I would describe it as a bit benign. Easy recovery and no noticeable hesitation. I did it intentionally with 1 up but the other 2 times were 2 up. All 3 times were at about half fuel load. It isn’t what I would say as prone to spinning IE doesn’t drop in at the drop of a hat. Hope that is of help. I thought the Aero restrictions came in after the catastrophic wing failure from Gross Overload during Aero’s and thus SB19. Cheers. Nige. From: Kristin Nowell Sent: Saturday, June 25, 2016 10:30 AM To: [email protected] Subject: [DOG mailing list] Spins Hi all, Our glider aerobat friend (Unlimited!) is coming to Maine for vacation, and is keen to fly in Tom's Dimona. Has anyone ever (unintentionally) spun it? Originally it was certified for aerobatics but then came 1985 SB 12 ( "Due to irregularities observed at spinning, further tests will be performed and until then the placard must be installed....), like what kind of irregularities? And either the tests were not done or not satisfactory as this operating restriction was never lifted, unlike those of service bulletin 18 ("glider flying prohibited!" "dual controlled instruction flights only"!), which were removed upon install of the wing latch kit (SB 19). Thanks Kristin
