Bob.
I might add to the excellent comments of the others that the spring engages only at around 13 degrees elevator up. Elevator down is no effect. I also might add that the force of the spring can not be overcome by the trim tab forces on the elevator. That means, even if you trim for let's say 40 MPH (assumed you could do that) then the plane will slow down only as much as the elevator spring allows it to do. THat is around 60 MPH - slower only by adding forces to the controls. This feature came in handy when I ones had my ASI quit on a flight. I just let my plane hang in there and knew I was making around 60 on approach. It also comes in handy when flying Hands off or letting your co pilot take the controls. You know the plane can be brought only into dangerously slow flight when someone overcomes the force of the spring. The spring is therefore a safety feature, not a convenience feature. Hartmut To: [email protected] From: [email protected] Date: Wed, 18 Feb 2009 21:23:49 -0600 Subject: Re: [ercoupe-tech] Elevator Return Spring Hi Bob, The spring you describe is 415-52026, and should be 18" long. It connects to one of three holes in a generally triangular steel "link", said "link" being connected to the elevator arm with the same bolt as pushrod that activates the elevator. When correctly adjusted, this spring should not interfere with trimming an airframe for hands off level flight between "cruise" (nose low) and "land" (nose high) positions. The range of elevator operation available without encountering the effect of this spring should be more than sufficient for normal flight. Its purpose is to provide a "feel" for a such rearward position of the yoke as should result in a power off 60 mph TAS glide. This position is NOT the rearmost position of the yoke available for flaring before touchdown at absolute minimum speed, as by increasing the rearward force on the yoke considerable additional "up" elevator is available before reaching the stop on the control wheel shaft. In normal "level" cruise flight, i.e. where the plane is neither climbing nor descending from a given altitude, the Ercoupe is in a subtle "nose down" configuration which also affords improved forward visibility. The design engine downthrust was incorporated to decrease the change in pitch between "power on" and "power off" operation with a propeller thrust line well above the centerline through the wing. Lynn's reference to ESM 35A for proper rigging is 100% correct, but many overlook the last sentence of 4.a.1. directing that the left panel of the split elevator is to be bent down 11-1/2º. While this should have been done in production, a replacement elevator may have been fitted without this having been done, and such an adjustment is has considerable effect in achieving the desired flight characteristics. A similar requirement to bend the entire trailing edge of elevators on 415-C, D and CD model Ercoupes downward 3º was found beneficial by Erco "to bring the airplane within the desired glide characteristics" per paragraph 15 of ESM 35, and was accomplished on Ercoupes effective about serial number 3882. It does appear there is a lapse in our parts and Service Manuals as to this spring. Regards, William R. Bayne .____|-(o)-|____. (Copyright 2009) -- On Feb 18, 2009, at 18:55, [email protected] wrote: Hey Bob: The best answer is contained in Ercoupe Service Memorandum 35A. It is a lower speed warning cushion. Apparently it was designed to provide a power off warning to help prevent the pilot from getting too slow in the landing approach in the model E,G and F Ercoupe. The flight test adjustment procedure requires changing the length of the spring to keep the power off airspeed at or slightly above 60 MPH with the pitch control back to the point where the spring causes additional force to be applied to the control. (obviously with the trim in full nose up condition) If you are getting a constant down pressure on the elevator, I would suggest checking the rigging in accordance with Memorandum 35A. The 46 415CD should not have this problem unless it has been modified with the split elevator and lower speed warning cushion spring. Lynn Nelsen In a message dated 2/18/2009 7:16:13 P.M. Eastern Standard Time, [email protected] writes: Group: Can anyone shed light on the purpose of a coiled spring 1/2" x 14" which attaches to the elevator bellcrank and to the bottom of the tail fuselage near the tiedown eyebolt? We have noted this spring being used on a 415E Ercoupe and a '57 Forney. It is not shown in either the repair manual or current Univair parts manual. It functions to place constant down pressure on the elevator causing a "nose down" orientation. Would the pilot have to overcome the pressure of this spring to maintain level flight? Could this conceivably be a modification to relieve the need for the engine to be canted down at a 3-1/2 degree angle below the nominal thrust line, in which case the aircraft would achieve hands off level flight? Any help with this apparent mystery would be appreciated. Thanks. Bob Blanchard N94676 - 415CD _________________________________________________________________ Get more out of the Web. Learn 10 hidden secrets of Windows Live. http://windowslive.com/connect/post/jamiethomson.spaces.live.com-Blog-cns!550F681DAD532637!5295.entry?ocid=TXT_TAGLM_WL_domore_092008
