X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 13 Mar 2011 21:07:50 -0400 Message-ID: X-Original-Return-Path: Received: from imr-da01.mx.aol.com ([205.188.105.143] verified) by logan.com (CommuniGate Pro SMTP 5.4c2) with ESMTP id 4905162 for lml@lancaironline.net; Sun, 13 Mar 2011 18:42:10 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.105.143; envelope-from=Sky2high@aol.com Received: from imo-da02.mx.aol.com (imo-da02.mx.aol.com [205.188.169.200]) by imr-da01.mx.aol.com (8.14.1/8.14.1) with ESMTP id p2DMfUeB019844 for ; Sun, 13 Mar 2011 18:41:30 -0400 Received: from Sky2high@aol.com by imo-da02.mx.aol.com (mail_out_v42.9.) id q.d84.14e33bb8 (45481) for ; Sun, 13 Mar 2011 18:41:24 -0400 (EDT) Received: from magic-d16.mail.aol.com (magic-d16.mail.aol.com [172.19.155.132]) by cia-mc06.mx.aol.com (v129.9) with ESMTP id MAILCIAMC068-b1a94d7d48143b9; Sun, 13 Mar 2011 18:41:24 -0400 From: Sky2high@aol.com X-Original-Message-ID: <17778.58a56883.3aaea214@aol.com> X-Original-Date: Sun, 13 Mar 2011 18:41:24 EDT Subject: Re: [LML] Old Lancair IV elevator trim tab incident X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_17778.58a56883.3aaea214_boundary" X-Mailer: AOL 9.6 sub 130 X-AOL-IP: 24.15.17.119 X-Spam-Flag:NO X-AOL-SENDER: Sky2high@aol.com --part1_17778.58a56883.3aaea214_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Fred, Good result, nice report, great warning...... I once demonstrated negative G's to my son and while pointing to the ignition key ring quickly ascending, the tow bar stowed behind the ignorant pilot's seat arose and smote the back of my pumpkin head. Duh! Thanks for the info even if I still rely on spring driven trim............. Scott In a message dated 3/13/2011 5:00:58 P.M. Central Daylight Time, fre derickmoreno@bigpond.com writes: Here is a head's up for owners of older Lancair IVs. My original kit is circa 1992 and came with the now-obsolete MAC 6A servo for the elevator trim tab. Returning from a big military-civil air show in Melbourne, Australia, we experienced an interesting incident that taught several lessons. The guy in the right seat was flying the airplane while we descended below an overcast, manuvering between rain showers toward our destination airport in the late morning. We were indicating about 180 KIAS with a few bumps when we got severely hammered with a violent down draft. Reconstructing the event it appears the following occurred: 1) The co-pilot's arm was raised off the arm rest. He hung onto the stick, but his hand slid up far enough to knock off the round pad at the top containing all the trim tab buttons. 2) Immediately following was a savage up push, probably arising when we exited the down draft. The co-pilot's arm was pulled down, but was moved off the arm rest and so continued downward while he was still holding he stick. Result: a big pull up. 3) Instinctive response when the nose went way up: he pushed down hard and we went negative G and everything hit the roof. 4) He handed the airplane over to me and I locked the stick in position to re-establish more or less horizontal flight and stop what was becoming a pilot induced oscillation. 5) Event over. Elapsed time about two to three seconds after which the guy in the back seat complained about something behind his back. Meanwhile holding horizontal flight required a large stick force nose down. The elevator trim tab was non-responsive. I slowed the airplane way down, put out gear and flaps, and landed in about 10 minutes holding the stick forward the entire time. The trim tab is somewhat larger than stock for the earlier models because of reports of insufficient trim in the pattern. The larger trim tab imposes a larger load on the servo. Result: 1) The hammer used to drive in the tie-downs and a fire extinguisher in the baggage compartment ended up in front of the rear seat back and behind the back of the guy sitting there. They had to migrate up and past several luggage bags to arrive at that location. 2) We found the trim tab could be moved up and down a bit when wiggled by hand. Clearly something in the servo was wrong. 3) We pulled the servo and found that the force on the trim tab during the upset had been enough to apply a compression load that broke the back side (thrust bearing side) of the trim servo out by breaking its containment grooves out as shown in the attached photo. This allowed the final driven gear on the push shaft to disengage from the gear train making it inoperative. We were still four hours from home, and so jury rigged a fix with cable ties and wire that worked for a while but ultimately slipped allowing the servo to fail again during the next descent (when further trimmed nose down). We finally locked the trim tab in place with some carved wood behind the servo and a lot of tape on the trim tab itself, made a couple of flights until we got it about right, and flew it home with a gentle tug on the stick while we trucked along staying below 170-180 KIAS. I wrote to Gary Menzimer at Ray Allen Company and found I was not the first to experience a servo failure in an older LIV during a severe upset. Another pilot had the same thing happen when a side window blew out the door on a P model, and probably pulled the pilot's arm out (and back on the stick) during the decompression. The fix: There is a direct replacement Ray Allen 7A servo that has been substantially modified to increase strength. Additionally, a sister company, Bristol S. G. Inc. offers a newer, much stronger and upgraded servo that is a near drop-in for the 6A-7A models dubbed the B6 series. See _www.bristolsg.com_ (http://www.bristolsg.com/) One can also purchase new clevis rod ends which are also significantly stronger than the earlier units. The jack screw exits the back of the box which may necessitate drilling a small hole in the elevator spar web, but otherwise it is a near drop - in installation. The Lessons: 1) The forecast included thunderstorms forming in the afternoon. We descended below the overcast after seeing some building cumulus but no thunderstorms during the late morning. We thought we had beat the strong convective activity. Wrong. Always be suspicious even when it is relatively smooth. An isolated down burst can ruin your whole day with no warning. 2) Keep your arm solidly on the arm rest to avoid unintentional stick movements. 3) Keep the baggage net spread over the baggage (non-P models). We got complacent during the long trip (seven hours going, seven and a half returning) and did not bother to pull it over everything. Result: some potentially dangerous stuff migrated forward of the rear seat back making for some uncomfortable seating back there. 4) If you have an old MAC servo in your elevator, consider an upgrade. The servos have moved forward two generations since the early 1990's and are much stronger which is appropriate for these fast airplanes. Fred -- For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html --part1_17778.58a56883.3aaea214_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
Fred,
 
Good result, nice report, great warning......
 
I once demonstrated negative G's to my son and while pointing to the= =20 ignition key ring quickly ascending, the tow bar stowed behind the ig= norant=20 pilot's seat arose and smote the back of my pumpkin head. =20 Duh! 
 
Thanks for the info even if I still rely on spring driven=20 trim.............
 
Scott
 
In a message dated 3/13/2011 5:00:58 P.M. Central Daylight Time,=20 frederickmoreno@bigpond.com writes:
Here is a head's up for owners of older Lancair IVs.
 
My original kit is circa 1992 and came with the now-obso= lete=20 MAC 6A servo for the elevator trim tab.  Returning from a=20 big military-civil air show in Melbourne, Australia, we exper= ienced=20 an interesting incident that taught several lessons.  The guy= in=20 the right seat was flying the airplane while we descended below an= =20 overcast, manuvering between rain showers toward our destination= airport=20 in the late morning.  We were indicating about 180 KIAS with= a few=20 bumps when we got severely hammered with a violent down=20 draft. 
 
 Reconstructing the event it appears the following=20 occurred:
1) The co-pilot's arm was raised off the arm rest. He hung on= to the=20 stick, but his hand slid up far enough to knock off the round pad= at the=20 top containing all the trim tab buttons.
2) Immediately following was a savage up push, probably arisi= ng=20 when  we exited the down draft.  The co-pilot's arm was= pulled=20 down, but was moved off the arm rest and so continued downward whi= le he=20 was still holding he stick.  Result: a big pull up.
3) Instinctive response when the nose went way up: he pushed= down=20 hard and we went negative G and everything hit the roof.
4) He handed the airplane over to me and I locked the st= ick in=20 position to re-establish more or less horizontal flight and stop= what=20 was becoming a pilot induced oscillation.
5) Event over.  Elapsed time about two to three seconds= after=20 which the guy in the back seat complained about something behind= his=20 back.  Meanwhile holding horizontal flight required a la= rge=20 stick force nose down.  The elevator trim tab was=20 non-responsive. 
I slowed the airplane way down, put out gear and flaps, and= landed=20 in about 10 minutes holding the stick forward the entire time.
 
The trim tab is somewhat larger than stock for the earlier mo= dels=20 because of reports of insufficient trim in the pattern.  The= larger=20 trim tab imposes a larger load on the servo.
 
Result:
1) The hammer used to drive in the tie-downs and a fire=20 extinguisher in the baggage compartment  ended up in fro= nt of=20 the rear seat back and behind the back of the guy sitting there.&n= bsp;=20 They had to migrate up and past several luggage bags to arrive at= that=20 location.
2) We found the trim tab could be moved up and down a bit=20 when wiggled by hand.  Clearly something in the servo wa= s=20 wrong.
3) We pulled the servo and found that the force on the= trim=20 tab during the upset had been enough to apply a compress= ion=20 load that broke the back side (thrust bearing side) of the trim se= rvo=20 out by breaking its containment grooves out as shown in the attach= ed=20 photo.  This allowed the  final driven gear on the push= shaft=20 to disengage from the gear train making it inoperative.
 
We were still four hours from home, and so jury rigged a fix= with=20 cable ties and wire that worked for a while but ultimately sl= ipped=20 allowing the servo to fail again during the next descent (when fur= ther=20 trimmed nose down).  We finally locked the trim tab in place= with=20 some carved wood behind the servo and a lot of tape on the trim ta= b=20 itself, made a couple of flights until we got it about right,= and=20 flew it home with a gentle tug on the stick while we trucked along= =20 staying below 170-180 KIAS.
 
I wrote to Gary Menzimer at Ray Allen Company and found I was= not=20 the first to experience a servo failure in an older LIV during a= severe=20 upset.  Another pilot had the same thing happen when a side= window=20 blew out the door on a P model, and probably pulled the pilot's ar= m out=20 (and back on the stick) during the decompression.
 
The fix:
There is a direct replacement  Ray Allen 7A servo that= has=20 been substantially modified to increase strength.  Additional= ly, a=20 sister company, Bristol S. G. Inc. offers a newer, much stronger= and=20 upgraded servo that is a near drop-in for the 6A-7A models dubbed= =20 the  B6 series.   See www.bristolsg.com&= nbsp;  One=20 can also  purchase new clevis rod ends which are also signifi= cantly=20 stronger than the earlier units.  The jack screw exits the ba= ck of=20 the box which may necessitate drilling a small hole in the elevato= r spar=20 web, but otherwise it is a near drop - in installation.
 
The Lessons:
 
1) The forecast included thunderstorms forming in the=20 afternoon.  We descended below the overcast after seeing some= =20 building cumulus but no thunderstorms during the late morning.&nbs= p; We=20 thought we had beat the strong convective activity.  Wrong.&n= bsp;=20 Always be suspicious even when it is relatively smooth.  = ; An=20 isolated down burst can ruin your whole day with no warning.=
2) Keep your arm solidly on the arm rest to avoid unintention= al=20 stick movements.
3) Keep the baggage net spread over the baggage (non-P=20 models).  We got complacent during the long trip (seven= hours=20 going, seven and a half returning) and did not bother to pull it= over=20 everything.  Result: some potentially dangerous stuff migrate= d=20 forward of the rear seat back making for some uncomfortable seatin= g back=20 there. 
4) If you have an old MAC servo in your elevator, consider an= =20 upgrade.  The servos have moved forward two generations since= the=20 early 1990's and are much stronger which is appropriate for these= fast=20 airplanes.
 
Fred
 
 
 
 
 


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