---------------------------------------------------------- Europa-List Digest Archive --- Total Messages Posted Tue 12/01/09: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 10:36 AM - MOTOGLIDER SPEEDBRAKE VIBRATION (ROBERT LINDSAY) 2. 11:50 AM - Halon Fire Extinguishers and Mandatory Permit Directive 2009..008 UK operators.... (Robert C Harrison) 3. 01:36 PM - Re: MOTOGLIDER SPEEDBRAKE VIBRATION (Bud Yerly) ________________________________ Message 1 _____________________________________ Time: 10:36:17 AM PST US From: "ROBERT LINDSAY" Subject: Europa-List: MOTOGLIDER SPEEDBRAKE VIBRATION During first flight with motor glider wings when speedbrakes were unlocked, brakes floated partially open. This, of course, is normal. However, occasionally at speeds btween 60 and 100 knots, the entire assembly would vibrate or shutter light to moderately as felt on the handle and visually evident on the speedbrakes themselves. Shutter frequency was much lower than the buzz of flutter and slight movement of the handle in either direction would stop the vibration. Suspect looseness in linikage or brake surface anomaly could be the cause. Anyone experience this and what was the fix? Bob Lindsay, test pilot for N911XS, Ramona and Warner Springs, California ________________________________ Message 2 _____________________________________ Time: 11:50:02 AM PST US From: "Robert C Harrison" Subject: Europa-List: Halon Fire Extinguishers and Mandatory Permit Directive 2009..008 UK operators.... Hi all! Just for info', today I checked with Fire Fighting Enterprises Ltd. Tel:- 0845 402 4242 www.ffeuk.com as to the likely compliance of my 0.7kg BCF Halon cylinder. Since mine originated in 2000 it only has one year to run, the limiting factor being 10 years total life span and/or 10% drop in weight of contents before service....and at that age it couldn't have been filled with the offending batch of Halon the subject of MPD 2009..008 concern anyway. I'm somewhat miffed that what seems to be a perfectly sound cylinder would need to be scrapped (unless the contents were carrying corrosive contamination when filled!) Of course since the "use in anger" factor is needed to be relied on no doubt our illustrious insurers may default on settlement of a claim if it is not in compliance. More expense! Regards Bob Harrison.G-PTAG ________________________________ Message 3 _____________________________________ Time: 01:36:20 PM PST US From: "Bud Yerly" Subject: Re: Europa-List: MOTOGLIDER SPEEDBRAKE VIBRATION Bob, This is common with a nicely built smooth operating airbrake linkage that is a little proud of the wing surface. One set on 13669 banged like hell. I changed out the bearings, sanded the inside of the airbrake so it would fit into the rebate with no contact, and it worked OK. Normally I don't deploy the airbrakes above 85 Knots. Pulling it above that speed is a bit of a workout. The flutter should stop by just holding the handle. If you are still getting a buzz when holding the handle, call me, because some thing is loose. Analysis is: When the airbrake handle is unlocked and released, the low pressure on the leading edge airbrake portion helps the airbrake start to deploy (especially if it is proud). The airbrake leading edge catches the wind and by the time the flap aft part compensates, it starts to close with a slap, but wait, it bounces open and catches air again...and repeats. To compensate for that, the bearings in the linkage are supposed to be MW4Ts. The T is for tight. When these bearings are installed, the system is not normally prone to flutter as the friction of these bearings prevents the ease of motion. The top leading edge of your airbrake needs a very sharp edge and an aft slope to also break the pressure buildup, and you probably have a slight contour which exacerbates the problem. This is a possible manufacturing flaw of the airbrake core and in the directions in airbrake construction, in my opinion, as the drawings make you feel that a nice curve is OK. The floxed corner on the leading edge of the upper surface should be sharp. After all, the core and photo's have a slight curve depicted and no note on the floxed corner. Your airbrake most probably sticks up a little when released on the ground and is forced closed by the linkage. When the brake is released, the airbrake instantly pops open due to contacting the inner rebate. This springy action is a problem as it can cause instant flutter even with the 4T bearings. If the airbrake is too fat for the rebate and sticks up proud of the surface, this too causes a low pressure area and a lifting force to the front of the airbrake. It seems that the rebate is not quite deep enough for a fully filled and painted surface unless great care is taken in fitting during construction. Nobody does that, we just build the airbrake and fill it, expecting it to fit. Flight Experience: In flight, at redline and a loose or low friction system, which sticks up proud of the wing surface will allow the airbrakes to bang quite a bit when just barely deployed and the handle released without the T bearings. This is quite startling if you are in a high speed dive and you bump the handle out of the lock. I have emailed for guidance on this common problem two years ago. Dave is now looking into the glider wing aerodynamics. The fix in the past was putting resistance into the system with the T bearings. I believe we will have to add holes to the airbrake portion (not unlike a WWII dive bomber airbrake) to relieve the pressure bubble that forms under the leading edge and the wing close out. The airbrake core will need to allow for a thinner underside to the leading edge of the airbrake core to allow a flush, interference free fit. We also must be very clear on the leading edge shape and do computer flow analysis and documentation. This is the same airbrake used on the Slingsby glider, which is supposed to be OK. I do not know about that personally, as I have not flown one. Other planes flying that I have tested are: N914PL, which only had a slight bounce, but no longer has the problem with the 4Ts installed, but 13669 was kind of exciting. Difference is the T bearings and fit, as I built both control surfaces with the clients, rigged them and test flew the planes. I have another motor glider in the shop which will get airbrake refinements (holes in the forward portion etc.). In the mean time, go to the hobby shop and tape a piece of 3 foot trailing edge stock (1 inch by 1/4 inch 90 degree triangle stock) to the bottom of the airbrake trailing edge. Tape it on with glider wing tape or similar and go fly. I find the extra up pressure makes deployment tougher, but it holds the airbrake closed and stops flutter until you can finish testing and get time to re-contour the airbrake for an interference free fit if necessary. If your airbrake sticks up on the leading edge, because it is too fat for the rebate, or springs open due to contact of the mechanism or rebate fit, I hate to tell you, but, de-skin the inside of the airbrake as appropriate and sand to re-contour until fit properly. This is how I fix it for my clients. Once it fits nicely in the slot and with the T bearings, it seems fine. Other comments are welcome. As I have only test flown two MGs extensively. Bud Yerly Custom Flight Creations. shop phone 813 653-4989 ----- Original Message ----- From: ROBERT LINDSAY To: europa-list@matronics.com Sent: Tuesday, December 01, 2009 1:32 PM Subject: Europa-List: MOTOGLIDER SPEEDBRAKE VIBRATION During first flight with motor glider wings when speedbrakes were unlocked, brakes floated partially open. This, of course, is normal. However, occasionally at speeds btween 60 and 100 knots, the entire assembly would vibrate or shutter light to moderately as felt on the handle and visually evident on the speedbrakes themselves. Shutter frequency was much lower than the buzz of flutter and slight movement of the handle in either direction would stop the vibration. Suspect looseness in linikage or brake surface anomaly could be the cause. Anyone experience this and what was the fix? Bob Lindsay, test pilot for N911XS, Ramona and Warner Springs, California www.aeroelectric.com www.buildersbooks.com www.homebuilthelp.com http://www.matronics.com/contribution http://www.matronics.com/Navigator?Europa-List ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message europa-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Europa-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/europa-list Browse Digests http://www.matronics.com/digest/europa-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.