---------------------------------------------------------- RV-List Digest Archive --- Total Messages Posted Wed 02/19/03: 27 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:08 AM - Re: wingtip tanks (Ralph E. Capen) 2. 06:29 AM - > Re: My First Oops (Oldsfolks@aol.com) 3. 07:00 AM - Re: Aileron squeeze (P M Condon) 4. 07:45 AM - Aileron squeeze (P M Condon) 5. 08:07 AM - Re: wingtip tanks (Robert Hasson) 6. 08:47 AM - Re: Grommets for firewall shields (Randall Henderson) 7. 09:18 AM - Re: missaligned holes (glenn williams) 8. 11:02 AM - Re: Wanted: Wooden Prop (RGray67968@aol.com) 9. 11:26 AM - MT Prop governor (Jeff Point) 10. 11:28 AM - Source for canopy bar grab handles (HCRV6@aol.com) 11. 12:08 PM - RV-8/8A towbars (Bill Marvel) 12. 12:14 PM - Artificial Horizon Questions (Bill Dube) 13. 12:28 PM - Re: Source for canopy bar grab handles (Dwpetrus@aol.com) 14. 01:05 PM - Re: MT Prop governor (Randy Lervold) 15. 01:25 PM - Re: MT Prop governor (Rhett Westerman) 16. 01:33 PM - Re: MT Prop governor (Stephen Johnson) 17. 03:02 PM - Re: Source for canopy bar grab handles (Jim Norman) 18. 05:11 PM - Snow in RV induction system, forced landing (Bob) 19. 05:22 PM - Snow in RV induction system, forced landing (corrected) (Bob) 20. 05:55 PM - Air Box Advisory (Bill Marvel) 21. 05:55 PM - Re: Artificial Horizon Questions (Tedd McHenry) 22. 06:02 PM - Propeller spacer (Rquinn1@aol.com) 23. 06:39 PM - Re: Air Box Advisory (RV6 Flyer) 24. 06:55 PM - Re: Air Box Advisory (Jerry Springer) 25. 08:10 PM - Re: Air Box Advisory (Sam Buchanan) 26. 09:16 PM - Air Box Advisory (C J Heitman) 27. 09:53 PM - Re: Air Box Advisory (Jerry Springer) ________________________________ Message 1 _____________________________________ Time: 06:08:33 AM PST US From: "Ralph E. Capen" Subject: Re: RV-List: wingtip tanks --> RV-List message posted by: "Ralph E. Capen" Jay, I've got a set of Johannsen tanks that I bought from Van's...9.5gal per side. I'm planning on adding two inspection ports on the underside of my wing...one inboard where the check valve is and the other outboard where the connection from the internal part of the wing to the actual tank is. I have the plumbing running from the bottom of the rib at the outboard side - a little higher as I cross through each rib towards the inboard side (to accoune for the dihedral angle of the wings. This will give me a very slight uphill ride to the check valve causing any water to roll downhill to be caught by the tip sump. The entry into the main tank is via a fitting that I will build in to the outboard rib of each main tank. My desire for their installation is purely a safety issue - I will be able to get into places and carry enough fuel to get back out for my trips...my bladder isn't good for the duration of the fuel I can carry. I've got some photo's - contact me offline... Ralph Capen -------Original Message------- From: jay pearlman Subject: RV-List: wingtip tanks > > --> RV-List message posted by: jay pearlman Anyone have experience with the johanson or other wingtip tanks - weight? best installation method? utility for cross country? > ________________________________ Message 2 _____________________________________ Time: 06:29:38 AM PST US From: Oldsfolks@aol.com Subject: RV-List: > Re: My First Oops --> RV-List message posted by: Oldsfolks@aol.com You were lucky to not ruin more parts. I was building the horizontal stabilizer and got to the point of drilling the skin. With the skin over the skeleton , I didn't discover ,until I took it off, that there was a little bow in the forward spar. The rivet holes ran out the edge on one side and into the radius of the spar in another place. I ordered parts to build another complete horizontal stabilizer . After that I took more care to be sure things were straight. Several other builders hung that skeleton in their shop as they started, so they could SEE how that thing goes together. That was a cloud with a silver lining . Keep on and look twice before you leap, Bob Olds A&P , EAA Tech. Counselor RV-4 , N1191X , Flying Now Charleston, Arkansas "Real Aviators Fly Taildraggers" ________________________________ Message 3 _____________________________________ Time: 07:00:35 AM PST US From: P M Condon Subject: RE: RV-List: Aileron squeeze --> RV-List message posted by: P M Condon Scott, what the % &%$% does "opposite aileron" mean ??? Didn't you mean "ever other aileron" ?? Seriously, "Opposite" meaning opposite of the heavy(heavy up or heavy down) aileron or vise-versa ? ////////////////////////////////////////////////////////////////////////////////// Time: 12:48:24 PM PST US From: "Van Artsdalen, Scott" Subject: RE: RV-List: Aileron squeeze --> RV-List message posted by: "Van Artsdalen, Scott" Squeeze the OPPOSITE aileron. I'm still going through this. Works like a charm. -- Scott VanArtsdalen Network Manager Union Safe Deposit Bank 209-946-5116 ________________________________ Message 4 _____________________________________ Time: 07:45:35 AM PST US From: P M Condon Subject: RV-List: Aileron squeeze --> RV-List message posted by: P M Condon First, be sure all rigging is proper and alignments are done correctly. Fairings add directional control, so be sure things are ok (and semiterical) in that department. Finally, the flaps can be adjusted to help with the problem you mention. Squeezing the ailerons is the last fine-tune kind of adjustment you want to make. Be sure all other surfaces are aligned and proper before yanking down on the ailerons. /////////////////////////////////////////////// Time: 12:13:05 PM PST US From: N13eer@aol.com Subject: RV-List: Aileron squeeze --> RV-List message posted by: N13eer@aol.com I have been through the archives and there are comments on which aileron to squeeze and what the effect is. But have seen post that says squeeze the heavy wing and ones that say squeeze the light one. Which is it? In my case with the spring trim centered, hands free the plane rolls to the left, which aileron do I squeeze? Alan Kritzman Cedar Rapids, IA RV-8 11 hours, with a wedge taped under the right aileron so I can fly straight. ________________________________ Message 5 _____________________________________ Time: 08:07:05 AM PST US From: "Robert Hasson" Subject: RE: RV-List: wingtip tanks --> RV-List message posted by: "Robert Hasson" Jay, I have been flying a set of Jon's tanks on my RV-6A for 2 1/2 years and 230 hours, and couldn't be happier with them. I installed them basically as per his instructions, except that I used 1/8" CherryMax rivets with 1" spacing. I also seated them into the wing with a copious amount of Epoxy resin thickened with mill fiber. They are now a permanent part of the wing! My reason for installing them is (in my opinion) 38 gallons of internal fuel doesn't provide a reasonable range when IFR reserves are considered. Having to shoot an approach just to get fuel every few hours wasn't something I was willing to accept. At altitude I routinely fly for 6 hours and still have a comfortable reserve. In a word they provide "options". The only problem I have had with the tanks is that during test flying, they would feed down about half way and then stop feeding. After landing, the remaining fuel would transfer into the mains!!!!!! It took two flights to figure out that the vents for the main tanks are within the prop wash and the tip tank vents are in the free air stream. Since the prop wash is at a higher airspeed than free stream, the head-pressure exerted on the fuel in the mains was higher than the head-pressure on the fuel in the tip tanks. After slightly reducing the angle on the front face of the main tank vents, the tips now feed completely. Since I installed my tanks during construction, I have no idea how much they increased the empty weight of the plane, and quite honestly.........don't care! I wanted the options they provide and was willing to pay the price, I would definitely do it again. If you want to see them installed, check out Sport Aviation, January 2003, pages 34-42. If you want to see them for yourself, look for me at Sun'nFun, AirVenture, or COPPERSTATE. Bob Hasson RV-6A N606BH -----Original Message----- From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matronics.com] On Behalf Of jay pearlman Subject: RV-List: wingtip tanks --> RV-List message posted by: jay pearlman Anyone have experience with the johanson or other wingtip tanks - weight? best installation method? utility for cross country? ________________________________ Message 6 _____________________________________ Time: 08:47:27 AM PST US From: "Randall Henderson" Subject: Re: RV-List: Grommets for firewall shields --> RV-List message posted by: "Randall Henderson" > If they are sized properly (tight fitting on the item) for the application > there's no need for RTV? I guess I'm thinking of those places where it can only fit so tight -- for example my starter wire (I have the solenoid on the inside of the firewall) goes with some other wires. The RTV is for that last little bit. Also split washers can tend to get pushed open a bit, and also wires/cables that goes through at an angle. Maybe I'm just too nit-picky about it? OTOH for safety we want to seal it up as well as we can, dont't we? BTW I sure like those swivel eyeball pass-throughs. Well worth the $$ IMHO. Randall Henderson, RV-6 N6R (~450 hrs) Portland, OR www.vanshomewing.org ________________________________ Message 7 _____________________________________ Time: 09:18:36 AM PST US From: glenn williams Subject: Re: RV-List: missaligned holes --> RV-List message posted by: glenn williams Drill through the existing hole in the top skin through the rib. If enough edge distance dimple and rivet if the edge distance protrudes into the hole you already drilled make a small square metal strip drill it and dimple it place on the back side of the rib and rivet it. if you have already dimpled the rib take a c-squeese with a flush rivet set and undo the dimple. Glenn Williams --- Bert Forero wrote: > --> RV-List message posted by: "Bert Forero" > > > Hello: > > I have a few missaligned holes on the top front > skin. > Best way to fix? fill with rivets, but i had to > filed them so sking be flush... > > Tought of J.B weld, not good, skin too thin.. > > > Any other suggestions.. > > > Thanks > > Bert > > rv6a > > Working on canopy > > Do Not Archive > > Sign up for Internet Service under $10 dollars a > month, at http://isp.BlueLight.com > > > > Contributions > any other > Forums. > > latest messages. > List members. > > http://www.matronics.com/subscription > http://www.matronics.com/FAQ/RV-List.htm > Digests:http://www.matronics.com/digest/rv-list > http://www.matronics.com/archives > http://www.matronics.com/photoshare > http://www.matronics.com/emaillists > > > > > ===== Glenn Williams 8A A&P N81GW ________________________________ Message 8 _____________________________________ Time: 11:02:18 AM PST US From: RGray67968@aol.com Subject: Re: RV-List: Wanted: Wooden Prop --> RV-List message posted by: RGray67968@aol.com In a message dated 2/18/03 12:03:33 PM Pacific Standard Time, rv_8pilot@hotmail.com writes: > I'm posting this for a Mustang II owner friend of mine. Please contact him > directly if you can help. > > Anyone have a spare prop for sale or loan to trouble shoot a vibration > problem, preferable a Warnke or Aymar Demuth for use on a 150hp Lyc with > 7/16 inch prop bolts. Might could use a prop for a 160hp. > > Thanks > > Greg Bordelon > email: gbordelon@hess.com > > > Bryan Jones -8 > Pearland, Texas Hi, I've got a 'spare' Warnke prop. Made by Bernie himself and one of his best Almost Constant Speed designs. It has 3/8 holes but could easily be drilled. Rick Gray RV6 in Ohio at the Buffalo Farm ________________________________ Message 9 _____________________________________ Time: 11:26:42 AM PST US From: Jeff Point Subject: RV-List: MT Prop governor --> RV-List message posted by: Jeff Point Does anyone have any knowledge or experience with the MT prop governor which Van's recently started selling? It is lighter and $300 cheaper according to Van's. http://www.vansaircraft.com/cgi-bin/catalog.cgi?ident=1045682284-436-519&browse=props&product=govnr_1 Jeff Point RV-6 finish kit Milwaukee WI ________________________________ Message 10 ____________________________________ Time: 11:28:45 AM PST US From: HCRV6@aol.com Subject: RV-List: Source for canopy bar grab handles --> RV-List message posted by: HCRV6@aol.com There recently was a company offering sliding canopy bar grab handles that did not require welding that had a web site under www.aircraftextras.com. Does anyone know if they are still around or how to get in touch with them, the web site has not been responding for several days? Do not archive Harry Crosby Pleasanton, California RV-6, starting firewall forward ________________________________ Message 11 ____________________________________ Time: 12:08:24 PM PST US From: Bill Marvel So Cal RV Group Subject: RV-List: RV-8/8A towbars --> RV-List message posted by: Bill Marvel I mentioned months ago that you can get a custom made RV-8/8A towbar from a metal shop out here in the L.A. area for (now price) $80. It is made of TIG welded aluminum rod and is designed to fit in the forward baggage compartment flush against the firewall. It is as large as it can be and still allow for the door to close. I have used mine for almost a year now and it works great. It us also very light. The shop owner is Glen Berringer and his number is 310 322 1627. I know him but am not in any way financially involved with this venture. He made the prototype up to my dimensions and the product works well. Bill Marvel -- Bill Marvel Home/office 310 832 7617 P.O. Box 784 Cell 310 293 2013 San Pedro, CA 90733 Fax 310 832 5334 One good deed beats 100 good intentions... ________________________________ Message 12 ____________________________________ Time: 12:14:21 PM PST US From: Bill Dube Subject: RV-List: Artificial Horizon Questions --> RV-List message posted by: Bill Dube I just got a Sperry J-6 Attitude gyro on Ebay for ten bucks. 1960 vintage, but pristine new old stock. Never been in an airplane. I connected it up to 400 Hz 3 phase and it seemed to spin up nicely. Here are the questions: 1) It seems to slowly drift to a slight "climb" attitude. Do I just need to let it "run in" or do I need to adjust or lube something? 2) It's been on the shelf since 1960, should I lube the bearings? What type lube is used. 3) It is drawing about 0.2 amps per phase. This seems a tad high to me. Is this within the normal range? 4) Where would I get a repair manual for this critter? ________________________________ Message 13 ____________________________________ Time: 12:28:48 PM PST US From: Dwpetrus@aol.com Subject: Re: RV-List: Source for canopy bar grab handles --> RV-List message posted by: Dwpetrus@aol.com I have a set that I will not be using that I would sell cheap. Call or email me offsite. Thanks, Wayne Petrus RV8A flying 318-322-4474 office ________________________________ Message 14 ____________________________________ Time: 01:05:34 PM PST US From: "Randy Lervold" Subject: Re: RV-List: MT Prop governor --> RV-List message posted by: "Randy Lervold" This governor is not manufactured by MT, but rather by Jihostroj (you're guess is as good as mine as to how to pronounce it) in the Czech Republic. MT resells them with their sticker on it, the Jihostroj placque is still attached. I saw one recently on the IO-540 that's going on the RV-10 prototype and it looked very nicely made from the outside. The factory web site is http://www.jihostroj.cz/JSWEB/pages/start/default.htm?Langx=gb but you won't learn much here. Another version (higher pressure) of this same governor is being sold by Whirl Wind propeller for use with their props, and especially their 150 which requires higher pressure to be properly controlled. You can contact WW for more info at 619-562-3725 or www.whirlwindpropellers.com. With Woodward being purchased by another company, with their prices then being raised signficantly, and with the apparent high quality of these new governors I have a feeling they are going to become more mainstream. Randy Lervold RV-8, 295 hrs, currently testing props EAA Technical Counselor www.rv-8.com ----- Original Message ----- From: "Jeff Point" Subject: RV-List: MT Prop governor > --> RV-List message posted by: Jeff Point > > Does anyone have any knowledge or experience with the MT prop governor > which Van's recently started selling? It is lighter and $300 cheaper > according to Van's. > http://www.vansaircraft.com/cgi-bin/catalog.cgi?ident=1045682284-436-519&bro wse=props&product=govnr_1 > > Jeff Point > RV-6 finish kit > Milwaukee WI > > ________________________________ Message 15 ____________________________________ Time: 01:25:26 PM PST US From: "Rhett Westerman" Subject: RE: RV-List: MT Prop governor --> RV-List message posted by: "Rhett Westerman" I have one of these governors on a GlaStar swinging an 82" Mt prop. Has about 60 hours on it and no problems. There were many advantages for me using this on the Glastar, one of which is the size. best, Rhett -----Original Message----- From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matronics.com]On Behalf Of Randy Lervold Subject: Re: RV-List: MT Prop governor --> RV-List message posted by: "Randy Lervold" This governor is not manufactured by MT, but rather by Jihostroj (you're guess is as good as mine as to how to pronounce it) in the Czech Republic. MT resells them with their sticker on it, the Jihostroj placque is still attached. I saw one recently on the IO-540 that's going on the RV-10 prototype and it looked very nicely made from the outside. The factory web site is http://www.jihostroj.cz/JSWEB/pages/start/default.htm?Langx=gb but you won't learn much here. Another version (higher pressure) of this same governor is being sold by Whirl Wind propeller for use with their props, and especially their 150 which requires higher pressure to be properly controlled. You can contact WW for more info at 619-562-3725 or www.whirlwindpropellers.com. With Woodward being purchased by another company, with their prices then being raised signficantly, and with the apparent high quality of these new governors I have a feeling they are going to become more mainstream. Randy Lervold RV-8, 295 hrs, currently testing props EAA Technical Counselor www.rv-8.com ----- Original Message ----- From: "Jeff Point" Subject: RV-List: MT Prop governor > --> RV-List message posted by: Jeff Point > > Does anyone have any knowledge or experience with the MT prop governor > which Van's recently started selling? It is lighter and $300 cheaper > according to Van's. > http://www.vansaircraft.com/cgi-bin/catalog.cgi?ident=1045682284-436-519&bro wse=props&product=govnr_1 > > Jeff Point > RV-6 finish kit > Milwaukee WI > > ________________________________ Message 16 ____________________________________ Time: 01:33:16 PM PST US From: "Stephen Johnson" Subject: Re: RV-List: MT Prop governor --> RV-List message posted by: "Stephen Johnson" This has my attention. I will be running the IO-360A1B6 and any weight savings up front would be welcome. Here's another reference from the MT web site: http://www.mt-propeller.com/en/governor.htm Steve Johnson RV-8 fuselage ----- Original Message ----- From: "Randy Lervold" Subject: Re: RV-List: MT Prop governor > --> RV-List message posted by: "Randy Lervold" > > This governor is not manufactured by MT, but rather by Jihostroj (you're > guess is as good as mine as to how to pronounce it) in the Czech Republic. > MT resells them with their sticker on it, the Jihostroj placque is still > attached. I saw one recently on the IO-540 that's going on the RV-10 > prototype and it looked very nicely made from the outside. The factory web > site is > http://www.jihostroj.cz/JSWEB/pages/start/default.htm?Langx=gb but you won't > learn much here. > > Another version (higher pressure) of this same governor is being sold by > Whirl Wind propeller for use with their props, and especially their 150 > which requires higher pressure to be properly controlled. You can contact WW > for more info at 619-562-3725 or www.whirlwindpropellers.com. > > With Woodward being purchased by another company, with their prices then > being raised signficantly, and with the apparent high quality of these new > governors I have a feeling they are going to become more mainstream. > > Randy Lervold > RV-8, 295 hrs, currently testing props > EAA Technical Counselor > www.rv-8.com > > > ----- Original Message ----- > From: "Jeff Point" > To: "RV List" > Subject: RV-List: MT Prop governor > > > > --> RV-List message posted by: Jeff Point > > > > Does anyone have any knowledge or experience with the MT prop governor > > which Van's recently started selling? It is lighter and $300 cheaper > > according to Van's. > > > http://www.vansaircraft.com/cgi-bin/catalog.cgi?ident=1045682284-436-519&bro > wse=props&product=govnr_1 > > > > Jeff Point > > RV-6 finish kit > > Milwaukee WI > > > > > > ________________________________ Message 17 ____________________________________ Time: 03:02:02 PM PST US From: "Jim Norman" Subject: RE: RV-List: Source for canopy bar grab handles --> RV-List message posted by: "Jim Norman" OK Listers... Here is my BIG TIP OF THE WEEK!!! I put in a canopy grab bar and it works great.... Love it... Great to have for "visitors"... give them something to grasp other than the fiberglass trim... I use it to get in and out...etc. BIG TIP: I made the grab bar out of a computer rack handle. If you have ever seen a computer server room at your local business, the computers often have these handles on each side. They are perfect size, AND, they are threaded for AN-3 bolts from the factory! Mine was plain aluminum, so I polished it to a mirror finish (like I did with a lot of my aluminum) and bolted it on. Thus.. no welding... just drill two holes through the forward canopy rail and bolt these dudes to the underside. THEN, put your fiberglass material over the bar like you have to do anyway. To tell the truth, I installed mine AFTER I already had the fiberglass strip installed... just made the hole in the glass bigger so the bolt head would go all the way down to the metal bar. Then I filled the holes in the glass with epoxy/microballoons... perfect. jim Tampa. -----Original Message----- From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matronics.com]On Behalf Of Dwpetrus@aol.com Subject: Re: RV-List: Source for canopy bar grab handles --> RV-List message posted by: Dwpetrus@aol.com I have a set that I will not be using that I would sell cheap. Call or email me offsite. Thanks, Wayne Petrus RV8A flying 318-322-4474 office ________________________________ Message 18 ____________________________________ Time: 05:11:43 PM PST US From: Bob Subject: RV-List: Snow in RV induction system, forced landing --> RV-List message posted by: Bob Listers, I want to share with you some information about the RV Filtered Air Box, learned from a most attention getting flight. Narrative: En route in level flight during snow it was observed that fuel flow had increased from about 9 gph to 11 gph. The engine was leaned, which returned the fuel flow to 9 gph or so, but the flow immediately started increasing to 10 gph. The engine was leaned again, the flow begin to increase again. It was observed that the manifold pressure had decreased from a nominal 23 inches to around 21 inches. Carb heat was applied, no significant effect was noted. Opening the throttle all the way increased the manifold pressure, but not to the value it had been when the flight first reached cruise altitude. The manifold pressure dropped another inch. At this point it was clear that something was amiss, and the flight was diverted to a nearby airport. Manifold pressure continued to drop. Switching tanks, operating with boost pump, and changing mixture settings caused no improvement. By the time the aircraft landed the engine was delivering almost no thrust, even though the throttle was wide open. When the throttle was pulled to idle in the flare, there was very little decrease in power (because very little power was being produced). The situation was discussed with two A&P/IAs, both of whom concluded that the problem was snow blocking the air intake filter. One of them, RV-8A builder Bill Marvel, will send a separate post to the list discussing my incident as well as another related to it. Verification: With all contamination removed from the FAB the engine ran normally. With some snow placed into the FAB, the engine ran very rough, producing lots of pop/bang noises, and not generating anything like full power. Examination revealed the snow had been drawn into the pleats of the air filter all around the perimeter of the air filter, effectively blocking air flow. It appears that the snow-blocked air filter starved the induction system of air and caused a super rich mixture. It appears the pop/bang sounds came from the unburned gas igniting in the exhaust system. Analysis: It appears that during the incident flight, snow was accumulating in the aircrafts Filtered Air Box (FAB), part of the RVs engine induction system. When the pilot selects carburetor (carb) heat in most general aviation aircraft the heated air flows into the induction system AFTER the air filter, so if the air filter is clogged the carb heat air will still reach the engine, allowing the engine to operate more or less normally. The RV FAB employs a non-standard induction system design. In the RV, carb heat air, when turned on, flows into the induction system IN FRONT OF the air filter. This means that a clogged air filter prevents carb heat air from flowing in to the engine, and the engine is starved of air. This appears to be a significant design problem. Detailed explanation of engine failure as experienced in flight: The blocked air filter impeded air flow into the carburetor, effectively applying a vacuum to the induction system. The lowered pressure in the induction system pulled excessive fuel from the carburetor venturi, causing the increase in fuel flow that was observed. In addition, the restricted airflow began to lower manifold pressure as the engine was deprived of sufficient air. When the engine was leaned the fuel flow temporarily returned to normal levels, but the increasing blockage of the air filter applied additional vacuum to the induction system, drawing more fuel through the carburetor, and increasing fuel flow again. When carb heat was applied the available warm air was insufficient to clear the accumulated snow in the air filter, and may have made the situation worse by melting snow crystals into ice/slush. Because of the design of the RV induction system, there was no way to bypass the clogged air filter and provide air to the engine. This resulted in a forced landing. A modified induction system, which will continue to provide air to the engine even after filter blockage, is shown at http://home.earthlink.net/~bob_rv. It has been flight tested, and appears to work well. Also see the new link about this problem on Vans web page, http://www.vansaircraft.com/pdf/airbox.pdf Bob ________________________________ Message 19 ____________________________________ Time: 05:22:05 PM PST US From: Bob Subject: RV-List: Snow in RV induction system, forced landing (corrected) --> RV-List message posted by: Bob Listers, I want to share with you some information about the RV Filtered Air Box, learned from a most attention getting flight. Narrative: En route in level flight during snow it was observed that fuel flow had increased from about 9 gph to 11 gph. The engine was leaned, which returned the fuel flow to 9 gph or so, but the flow immediately started increasing to 10 gph. The engine was leaned again, the flow begin to increase again. It was observed that the manifold pressure had decreased from a nominal 23 inches to around 21 inches. Carb heat was applied, no significant effect was noted. Opening the throttle all the way increased the manifold pressure, but not to the value it had been when the flight first reached cruise altitude. The manifold pressure dropped another inch. At this point it was clear that something was amiss, and the flight was diverted to a nearby airport. Manifold pressure continued to drop. Switching tanks, operating with boost pump, and changing mixture settings caused no improvement. By the time the aircraft landed the engine was delivering almost no thrust, even though the throttle was wide open. When the throttle was pulled to idle in the flare, there was very little decrease in power (because very little power was being produced). The situation was discussed with two A&P/IAs, both of whom concluded that the problem was snow blocking the air intake filter. One of them, RV-8A builder Bill Marvel, will send a separate post to the list discussing my incident. Verification: With all contamination removed from the FAB the engine ran normally. With some snow placed into the FAB, the engine ran very rough, producing lots of pop/bang noises, and not generating anything like full power. Examination revealed the snow had been drawn into the pleats of the air filter all around the perimeter of the air filter, effectively blocking air flow. It appears that the snow-blocked air filter starved the induction system of air and caused a super rich mixture. It appears the pop/bang sounds came from the unburned gas igniting in the exhaust system. Analysis: It appears that during the incident flight, snow was accumulating in the aircraft's Filtered Air Box (FAB), part of the RV's engine induction system. When the pilot selects carburetor (carb) heat in most general aviation aircraft the heated air flows into the induction system AFTER the air filter, so if the air filter is clogged the carb heat air will still reach the engine, allowing the engine to operate more or less normally. The RV FAB employs a non-standard induction system design. In the RV, carb heat air, when turned on, flows into the induction system IN FRONT OF the air filter. This means that a clogged air filter prevents carb heat air from flowing in to the engine, and the engine is starved of air. This appears to be a significant design problem. Detailed explanation of engine failure as experienced in flight: The blocked air filter impeded air flow into the carburetor, effectively applying a vacuum to the induction system. The lowered pressure in the induction system pulled excessive fuel from the carburetor venturi, causing the increasein fuel flow that was observed. In addition, the restricted airflow began to lower manifold pressure as the engine was deprived of sufficient air. When the engine was leaned the fuel flow temporarily returned to normal levels, but the increasing blockage of the air filter applied additional vacuum to the induction system, drawing more fuel through the carburetor, and increasing fuel flow again. When carb heat was applied the available warm air was insufficient to clear the accumulated snow in the air filter, and may have made the situation worse by melting snow crystals into ice/slush. Because of the design of the RV induction system, there was no way to bypass the clogged air filter and provide air to the engine. This resulted in a forced landing. A modified induction system, which will continue to provide air to the engine even after filter blockage, is shown at http://home.earthlink.net/~bob_rv. It has been flight tested, and appears to work well. Also see the new link about this problem on Van's web page, http://www.vansaircraft.com/pdf/airbox.pdf Bob ________________________________ Message 20 ____________________________________ Time: 05:55:25 PM PST US From: Bill Marvel So Cal RV Group Subject: RV-List: Air Box Advisory --> RV-List message posted by: Bill Marvel All RVers: Recently an Air Box Advisory was posted on Vans web site regarding the use of carb heat and an upcoming modification to the FAB kit. Earlier today a post was made on the Matronics list regarding a dead stick landing subsequent to engine failure while flying in snow. These two events are related. I know Bob, the pilot involved in this incident, and he called to advise me of what had taken place and to seek my help in understanding it. I have some experience and background in this area and for that reason I am writing this post to make you fully aware of the importance of the forthcoming FAB modification. As he explained in his email to the RV list, Bobs aircraft was flying in snow when he noted an increase in fuel flow without having touched the mixture control. Leaning the mixture reduced the fuel flow, which 30 seconds later inexplicably began another increase. Shortly thereafter the manifold pressure began to decrease and he started a divert to the nearest airport. The aircraft was unable to maintain altitude with the power loss but was fortunate to be within an attainable distance of a suitable landing spot. After landing, Bob made an inspection of the airplane in order to determine what had happened. There was no evidence of any damage anywhere, but he did note that there was some snow in the air box. He made a number of engine runs on the ground after this snow was removed and found that the engine operated normally. There were no mechanical problems. However, in subsequent ground testing of the engine with increasing amounts of snow added to the air box, he experienced results similar to the failure mode and found that the engine would run rough with popping and backfiring sounds in the exhaust. This was a virtual confirmation of a scenario I was concerned with in the recent past. I became aware of a potential problem in the design of the FAB kit that is provided for all of our airplanes. I told a few friends about it and went so far as to alert Vans about my concerns. It is a great credit to Van that his airplanes are so useful that they are being operated increasingly as transportation machines, including flights in IMC weather. But doing so opens a trap for the unwary regarding the current air box design. I doubt that most aircraft builders would have any idea whatsoever about the following potential problem inherent in air box kit as it now exists. In air box designs for certified aircraft, whether fuel injected or carbureted, the air flow via carb heat or alternate air goes direct to the engine from the selected source and most important, BYPASSES THE AIR FILTER. This is a very standardized feature. In fact, the POH pre-takeoff section will almost always caution the pilot to minimize the duration of the carb heat/alternate air check on the ground because it allows unfiltered air into the engine. In the case of carb heat, when it is selected, two things are supposed to occur simultaneously. One is that the cold inlet air flow is stopped, and two is that a heated flow is supposed to open to the carburetor, through a path that bypasses the air filter. Note that I said "open to the carburetor." This heated flow is not a pressurized blast of hot air like a flame thrower, going in and melting ice. The suction of the engine intake system through the carburetor is what brings the hot air into the carb for deice. If for any reason this suction does not occur, the hot air flow path will soon be worthless because the engine will quit and along with it the source of heat. And therein lies the problem. In the air box design used in the RV kits, hot air is made available at the front of the air box, just behind the cold air induction opening in the cowling. Therefore, it must first pass THROUGH the air filter before reaching the carburetor instead of bypassing the air filter as is the standard arrangement. This is a trap for a pilot who successfully checks carb heat before takeoff and then flies into something that blocks the air filter, which in this design also blocks the alternate source of air that otherwise would bypass the air filter when called for by activation of the carb heat control. This single point failure mode causes the pilot to lose not only the hot air for carb ice prevention, but also the air the engine needs for combustion. What I believe caused the engine failure in Bobs incident should now be clear. The snow that he was flying through just before the problem occurred was entering the airbox, which is thermally isolated from the engine. It is fiberglass and is operating at near the outside air temperature. In short, the air filter was at the same temperature as the snow that was gradually plugging it up. When the air filter became so restricted by snow sucked into it by the intake vacuum that the engine could no longer get enough air, it began to run rough. He no doubt turned on carb heat, expecting it to work and in a normal induction system it would have. However, since suction is required to pull the heated air into the engine, and since suction was no longer available due to the clogged air filter, the heated air had nowhere to go. Had the design employed a different path that bypassed the air filter, the engine would have had all the heated air it needed and would have continued to operate. As to the rough running engine experienced by Bob during ground tests, there is an explanation which is backed up by his observed data. Since the induction system is still pulling a strong vacuum behind the snow clogged air filter and there is no air incoming to relieve that vacuum, the only thing left to do so is the fuel inlet. Block the air flow outside of the carburetor and put a strong vacuum on the fuel nozzle in the carburetor venturi and it will pull out lots of fuel -- the very thing Bob noticed on his fuel flow gauge at the beginning of his engine loss scenario. He leaned the mixture to decrease the flow to normal but noted it rising again. This is the expected result of increased air flow blockage and the resulting added suction on the fuel nozzle. When this very rich mixture gets into the cylinders and exhaust system, with spark plugs still operating, it is going to fire but not produce normal power. Ignition may well be taking place in the fuel laden exhaust pipes as well as in the cylinders as the exhaust fumes meet outside air. This is what caused the engine popping and backfiring sounds. In any event, I believe that few builders will know about this on their own and simply modifying the design of the kit would prevent the problem from occurring entirely. That is the importance of the new FAB Advisory on the web site and the upcoming modification drawings. If you are using the existing air box, you should understand its inherent design shortcoming and resulting limitations. As a minimum, know this problem exists. If flying in moisture, you might want to consider operating continuously with full carb heat. If you wait until symptoms indicate that you need it, there wont be any heat available for you to have. Unfortunately, insufficient carb heat can also lead to carb ice, which can be as bad as a plugged up air filter. The current unmodified design, which leads to heat loss through the air filter and a potential cessation of flow altogether, is really quite problematic in the event of an encounter with any type of air filter obstruction. Vans has acted responsibly in addressing this matter and we owe it to them to incorporate the modification or at least understand the implications if we dont. My respect and admiration for Van and his company, always great, is now just that much more. Please spread the word on this. Not everyone has computers yet. Lets be safe out there and lets learn more every day. Bill Marvel -- Bill Marvel Home/office 310 832 7617 P.O. Box 784 Cell 310 293 2013 San Pedro, CA 90733 Fax 310 832 5334 One good deed beats 100 good intentions... ________________________________ Message 21 ____________________________________ Time: 05:55:25 PM PST US From: Tedd McHenry Subject: Re: RV-List: Artificial Horizon Questions --> RV-List message posted by: Tedd McHenry > 1) It seems to slowly drift to a slight "climb" attitude. It just wants to go flying. Forty-three years is a long time to sit on the shelf. Tedd McHenry Surrey, BC ________________________________ Message 22 ____________________________________ Time: 06:02:03 PM PST US From: Rquinn1@aol.com Subject: RV-List: Propeller spacer --> RV-List message posted by: Rquinn1@aol.com I have a 2 1/4" Sensenich spacer for sale. The spacer is in near new condition but I cannot use it because my engine crankshaft flange needs 7/16 inch bolts and this spacer is for 3/8 inch bolts. The spacer new costs $160.00. I will sell this one for half price or $80.00. (Buyer pays shipping cost) Please reply to: RQuinn1@aol.com Thanks Rollie & Rod RV6A N799RQ ________________________________ Message 23 ____________________________________ Time: 06:39:23 PM PST US From: "RV6 Flyer" Subject: Re: RV-List: Air Box Advisory --> RV-List message posted by: "RV6 Flyer" Bill and Bob: My standard operating procedure for the past 5+ years was to turn Carb Heat on whenever in any precipitation. During flight tests, my induction system (FAB320) did not meet FAR 23.1093 (a)(1). Since it is an Experimental Aircraft, it does not need to meet FAR 23. An old FAA employee once told me, In God we trust, everything else we check. I think Van did a great job in the design of the RV. I make my living TESTING so I tested everything on my airplane. I recommend that everyone test and inspect everything taking nothing for granted. I am listed as Manufacturer on the FAA Registry and as such am responsible for the proper operation of all aircraft systems. How do we know they operate properly unless we test them? Bills idea of carb heat bypassing the filter may allow more heat into the carb. Have not had any carb ice or induction problems the way I operate the airplane. Have not done any tests flying in snow, ice, or freezing rain, as I do not intend to fly in those conditions. That does not mean I will not encounter problems in conditions that I have not tested for. There is always the possibility that I could end up in conditions I have no intention of being in and the filter bypass would be a good thing. Gary A. Sobek "My Sanity" RV-6 N157GS O-320 Hartzell, 1,255 + Flying Hours So. CA, USA http://SoCAL_WVAF.rvproject.com ________________________________ Message 24 ____________________________________ Time: 06:55:38 PM PST US From: Jerry Springer Subject: Re: RV-List: Air Box Advisory --> RV-List message posted by: Jerry Springer Bill Marvel wrote: > --> RV-List message posted by: Bill Marvel > > All RVers: > > Recently an Air Box Advisory was posted on Vans web site regarding the > use of carb heat and an upcoming modification to the FAB kit. > *Long post snipped* Appreciate the time you are taking to post the information BUT, flying in that type of situation should have triggered the use of carb heat earlier than it sounds like it was applied. If Carb heat had been used sooner it probably would have melted any build up and also would have blocked further ingestion of snow. Jerry ________________________________ Message 25 ____________________________________ Time: 08:10:35 PM PST US From: Sam Buchanan Subject: Re: RV-List: Air Box Advisory --> RV-List message posted by: Sam Buchanan Bill Marvel wrote: > > --> RV-List message posted by: Bill Marvel > I became aware of a potential problem in the design of the FAB kit that > is provided for all of our airplanes. I told a few friends about it and > went so far as to alert Vans about my concerns. It is a great credit > to Van that his airplanes are so useful that they are being operated > increasingly as transportation machines, including flights in IMC > weather. But doing so opens a trap for the unwary regarding the current > air box design. I doubt that most aircraft builders would have any idea > whatsoever about the following potential problem inherent in air box kit > as it now exists. The design/flaws of the Vans airbox as stated in the above post has been obvious to many builders. While I never intend to fly my RV-6 in conditions that remotely resemble icing conditions, or even snow for that matter, since the day I first saw the airbox I have been concerned about the ramifications of snarfing a bird into the air intake. I am interested in seeing how Vans addresses this issue. I must admit however, that in my opinion, flying any RV into icing conditions is far, far beyond the design intentions of this series of aircraft. When Van designed his marvelous little aircraft, he intended for them to be light, efficient sport vehicles to be enjoyed by pilots in VMC. I'm trying hard not to sound preachy, but while I still have an interest in using my RV-6 in IMC, I must realize that to do so is to take the aircraft into a flight regime for which it was not intended by the designer, and I must be cognizant of the associated risks. Sam Buchanan ________________________________ Message 26 ____________________________________ Time: 09:16:20 PM PST US From: "C J Heitman" Subject: RV-List: Air Box Advisory --> RV-List message posted by: "C J Heitman" With all the talk about the air box, I decided to add a page to my website showing details of my spring-loaded alternate air door. I have Bendix injection, so I do not need carb heat, but a similar door my work on a carbureted engine (in addition to carb heat). Here is the link: http://my.execpc.com/~cjh/altair.html Note: Snow is not the only hazard that could make this door useful. There are many birds around my airstrip. I was picturing one of them stuffed into my air intake when I designed my alternate air door. Chris Heitman Dousman WI RV-9A N94ME (reserved) http://my.execpc.com/~cjh/rv9a.html http://www.pegasusautoracing.com/ --- ________________________________ Message 27 ____________________________________ Time: 09:53:44 PM PST US From: Jerry Springer Subject: Re: RV-List: Air Box Advisory --> RV-List message posted by: Jerry Springer I have just a little bit of a problem with that design and that is VIBRATION. I know how much those hinges can wear and possibility of some small part gong directly to the carb or fuel injection intake. I have replaced the hinges on my alternate air source on the FAB-360 because I was not comfortable with how loose the hinges were getting. YMMV Probably never happen but needs to be watched. Jerry --------------------------- C J Heitman wrote: > --> RV-List message posted by: "C J Heitman" > > With all the talk about the air box, I decided to add a page to my website > showing details of my spring-loaded alternate air door. I have Bendix > injection, so I do not need carb heat, but a similar door my work on a > carbureted engine (in addition to carb heat). > > Here is the link: http://my.execpc.com/~cjh/altair.html > > Note: Snow is not the only hazard that could make this door useful. There > are many birds around my airstrip. I was picturing one of them stuffed into > my air intake when I designed my alternate air door. > > Chris Heitman > Dousman WI > RV-9A N94ME (reserved) > http://my.execpc.com/~cjh/rv9a.html > http://www.pegasusautoracing.com/ > --- > > > > > > >