X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 26 Jun 2008 21:50:45 -0400 Message-ID: X-Original-Return-Path: Received: from vms173001pub.verizon.net ([206.46.173.1] verified) by logan.com (CommuniGate Pro SMTP 5.2.4) with ESMTP id 2991867 for lml@lancaironline.net; Thu, 26 Jun 2008 00:48:58 -0400 Received-SPF: pass receiver=logan.com; client-ip=206.46.173.1; envelope-from=tom.gourley@verizon.net Received: from jacky0da39824a ([71.111.136.42]) by vms173001.mailsrvcs.net (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) with ESMTPA id <0K31001LEZZQ8D07@vms173001.mailsrvcs.net> for lml@lancaironline.net; Wed, 25 Jun 2008 23:47:54 -0500 (CDT) X-Original-Date: Wed, 25 Jun 2008 21:47:43 -0700 From: "Tom Gourley" Subject: [LML] Emergency gear extension (Was: Reply to parts needed) X-Original-To: "Lancair Mailing List" Reply-to: "Tom Gourley" X-Original-Message-id: <000901c8d747$c6978dd0$650610ac@jacky0da39824a> MIME-version: 1.0 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.3198 X-Mailer: Microsoft Outlook Express 6.00.2900.3138 Content-type: multipart/alternative; boundary="----=_NextPart_000_0006_01C8D70D.195B0000" X-Priority: 3 X-MSMail-priority: Normal References: This is a multi-part message in MIME format. ------=_NextPart_000_0006_01C8D70D.195B0000 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Excerpt from Steve Young's mail: "When I got close to home I turned on the avionics and the master switch = on to see if the gear would go down. I felt the right one lock down and = then everthing when dead. .... I opened the dump valve and pulled the curcuit breaker at this time. I = went through the procedures with no luck. I was thinking at the time = that I needed to stay at the 120 knots so I would take the doors off. = Hind sight is always 20/20 and I should have been alot more aggressive. = I wish now, I would have climbed higher and build more speed prior to = the yawing since I lost the gear door anyway on landing." For the last several years I've been flying a Commander 112 which has a = gear system nearly identical to the Legacy; i.e. an electric motor = drives a hydraulic pump which operates the landing gear. Just like the = Legacy, and as far as I know the 320/360, the gear is held up by = hydraulic pressure and emergency extension uses a simple dump valve to = relieve pressure in the gear hydraulic cylinders. Gravity starts the = gear down and springs, rather than gas struts, finishes the gear = extension and locks the over-center links in place. I've had to use the = dump valve twice in flight. The first time the gear failed to extend = when attempting to land at an airport about 30 min from my home base. I = flew back home, slowed to about 90 kts before entering downwind (normal = approach for the 112 is 80 KIAS) and activated the dump valve. The gear = came down just like when it was on jacks during the annual inspection = (you do check the emergency extension at least yearly, right?), I got 3 = green and landed with no problems. After getting back to the hangar we = put the plane on jacks and, of course, the gear worked just fine; could = not get it to fail. But like the old saying goes, problems that go away = by themselves come back by themselves. =20 About 100 flying hours later the gear failed to extend, again. This = time I didn't slow down as much before hitting the dump valve. (Max = gear extension speed on the 112 is 130 KIAS.) Like before the mains = came down immediately. (They're pretty heavy and actually free fall = faster than the normal extension.) The nose gear takes a little longer, = but this time it didn't come all the way down; no green nose gear light. = I tried pulling a couple of G's but no luck. (My wife was with me so I = didn't want to pull too hard.) But as I slowed below 100 KIAS and = started extending the flaps the nose gear locked in place. At this = point I started breathing again. Once again the landing was uneventful, = but this time back in the hangar and on the jacks the gear motor refused = to run at all. =20 After replacing the motor/pump assembly we ran some extension = experiments and came to two conclusions. First, the main gear does not = appear to be sensitive to airspeed during an emergency extension, but = the nose gear does. Slower is better. Unless you've lost the engine = you can always speed up and yaw if you need more force on the main gear = doors to lock the mains in place, but let the nose gear lock first. = Second, emergency extension worked better, i.e. was more positive, when = we started with the gear fully retracted. Starting a normal gear = extension then killing power with the gear partially extended, then = hitting the dump valve didn't always result in positive gear extension, = even when sitting on jacks. We also ended up replacing the nose gear = springs and got more positive extension on the nose gear, so check your = gas struts regularly. Granted this was all on a Commander 112, not a Lancair, but due to the = similar gear systems I think the rules I've set for myself for emergency = extension on the 112 may also work on the Legacy and 320/360: 1) Slow = down as much as possible before activating the dump valve. This makes = it easier to extend the nose gear. 2) If you are having electrical = problems don't even try to do a normal extension. Leave the gear fully = retracted then pull the gear breaker and use the dump vavle. Of course trying this out at a safe altitude in your own plane is highly = recommended. Your mileage may vary. Tom Gourley ------=_NextPart_000_0006_01C8D70D.195B0000 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Excerpt from Steve Young's = mail:
"When I got close to home I turned = on the=20 avionics and the master switch on to see if the gear would go down. = I felt=20 the right one lock down and then everthing when dead.
....
I opened the dump valve and pulled = the curcuit=20 breaker at this time. I went through the procedures with no luck. I was = thinking=20 at the time that I needed to stay at the 120 knots so I would take the = doors=20 off. Hind sight is always 20/20 and I should have been alot more = aggressive. I=20 wish now, I would have climbed higher and build more speed prior to the = yawing=20 since I lost the gear door anyway on landing."
 
For the last several years I've been = flying a=20 Commander 112 which has a gear system nearly identical to the Legacy; = i.e. an=20 electric motor drives a hydraulic pump which operates the landing = gear. =20 Just like the Legacy, and as far as I know the 320/360, the gear is held = up by hydraulic pressure and emergency extension uses a simple dump = valve=20 to relieve pressure in the gear hydraulic cylinders. =20 Gravity starts the gear down and springs, rather than gas struts, = finishes=20 the gear extension and locks the over-center links in place.  = I've had=20 to use the dump valve twice in flight.  The first time the gear = failed to=20 extend when attempting to land at an airport about 30 min from my home=20 base.  I flew back home, slowed to about 90 kts before = entering=20 downwind (normal approach for the 112 is 80 KIAS) and activated the = dump=20 valve.  The gear came down just like when it was on = jacks during=20 the annual inspection (you do check the emergency extension at least = yearly,=20 right?), I got 3 green and landed with no problems.  After getting = back to=20 the hangar we put the plane on jacks and, of course, the gear worked = just fine;=20 could not get it to fail.  But = like the old=20 saying goes, problems that go away by themselves come back by = themselves. =20
 
About 100 flying hours later the gear = failed to=20 extend, again.  This time I didn't slow down as much before hitting = the=20 dump valve.  (Max gear extension speed on the 112 is 130 = KIAS.)  Like=20 before the mains came down immediately.  (They're pretty heavy and = actually=20 free fall faster than the normal extension.)  The nose gear takes a = little=20 longer, but this time it didn't come all the way down; no green nose = gear=20 light.  I tried pulling a couple of G's but no luck.  (My wife = was=20 with me so I didn't want to pull too hard.)  But as I = slowed=20 below 100 KIAS and started extending the flaps the nose gear locked in=20 place.  At this point I started breathing again.  Once again = the=20 landing was uneventful, but this time back in the hangar and on the = jacks the=20 gear motor refused to run at all.  
 
After replacing the motor/pump assembly = we ran=20 some extension experiments and came to two conclusions.  = First, the=20 main gear does not appear to be sensitive to airspeed during an = emergency=20 extension, but the nose gear does.  Slower is=20 better.  Unless you've lost the engine you can always speed up = and yaw=20 if you need more force on the main gear doors to lock the mains in = place, but=20 let the nose gear lock first.  Second, emergency extension = worked=20 better, i.e. was more positive, when we started with the gear fully = retracted.  Starting a normal gear extension then killing power = with the=20 gear partially extended, then hitting the dump valve didn't always = result in=20 positive gear extension, even when sitting on jacks.  We also ended = up=20 replacing the nose gear springs and got more = positive extension on the=20 nose gear, so check your gas struts regularly.
 
Granted this was all on a Commander = 112, not a=20 Lancair, but due to the similar gear systems I think the rules I've set = for=20 myself for emergency extension on the 112 may also work = on the=20 Legacy and 320/360:  1) Slow down as much as possible before = activating the=20 dump valve.  This makes it easier to extend the nose gear.  2) = If you=20 are having electrical problems don't even try to do a normal = extension. =20 Leave the gear fully retracted then pull the gear breaker and use the = dump=20 vavle.
 
Of course trying this out at a safe = altitude in=20 your own plane is highly recommended.  Your mileage may = vary.
 
Tom Gourley
 
 
------=_NextPart_000_0006_01C8D70D.195B0000--