REFLECTOR:Follow up on my bad landing

Ronnie Brown reflector@tvbf.org
Tue, 6 Apr 2004 14:52:46 -0400


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THANKS for sharing Don!!!

I have had two instances where the gear did not go down as commanded.  =
The first time it was cold (32) at take off and warmer when I landed =
about 30 minutes later.  But the 2nd time it was 70 degrees at take off =
and landing. As soon as I hit the reset button, all worked as it was =
supposed to.=20

I'm guessing that there is a piston seal(s) that are leaking a bit and =
allowing pressure to bleed from the high side to the low side.  And the =
way the electro-hydraulic pump works, there is a pressure relief valve =
on both the up side and down side that is supposed to relieve excess =
pressure (3000 psi on high side and something lower on the low side).  =
This is from reading the repair manual for these pumps.  On marine out =
drive applications, they don't use any pressure switches - just the =
relief valves. If you run the outdrive too far up or down, the pump =
keeps running but excess pressure is relieved. I think the low pressure =
side has something more than zero pressure on it after the gear is =
retracted, and it doesn't take much of a leak from high to low side to =
trip the low side pressure switch.  I didn't put a pressure gauge port =
on the low side so I can't verify this.  Perhaps someone who has both hi =
and low side gauges installed can confirm or refute these pressures.

Not trying to preach but I try to always put my gear down at mid field =
or if on a straight in at the initial approach fix - IAF 5 miles out.  =
Same place EVERYTIME!!!  Then I look at my green lights and call out to =
myself out loud that I have two green lights on short final.  Now let me =
find some wood to knock on - here it is - knocking on skull.  (:^))=20

Hope you get into the air soon!!!!

Ronnie
  ----- Original Message -----=20
  From: Donald Royer=20
  To: reflector@tvbf.org=20
  Sent: Tuesday, April 06, 2004 2:07 PM
  Subject: REFLECTOR:Follow up on my bad landing



  I promised more information on my bad landing last week as soon as I =
had more information. After thinking more about what happened and =
talking to several eye witnesses who between them saw all of the =
incident, I can say with some confidence exactly what happened.

  First , if was not a gear collapse, it was a gear up landing. What =
initially confused the situation was when the plane can to a stop, the =
gear was out of the gear wells and resting on the ground. In addition =
the gear switch was in the down position. However, a pilot who was out =
walking his dog at the appropriate end of the runway and who saw the =
final approach and touchdown was quite sure that the gear was in the =
wells at the time of touchdown. That information along with the =
information that I reported before that I was distracted enough that I =
really could not say whether I had two greens or not, but that I would =
in all probability have seen the red gear unsafe light if it had been on =
seems to lead to one conclusion.

  The only scenario that I could come up with the fits everything is the =
following. I put the gear switch down at the appropriate time but then =
nothing happened. This possibility has been discussed here on the =
Reflector before and in fact I have installed the little circuit to =
bypass the down pressure switch to get out of this condition. Then, the =
shock of the landing jarred the system out or the hang up and the gear =
tried to extend as I was sliding down the runway. This conclusion is =
also supported by the fact that I heard the gear horn at about ten feet. =
My simultaneous reaction was to think that the gear warning system was =
malfunctioning again as it had several times recently, and before I got =
around to considering that it might be telling me the truth this time, I =
was on the ground.

  I put the cause to be a combination of a known flaw in the system and =
pilot error. I simply did not notice that the gear had not extended when =
it should have. In my defense, I was distracted at the time, it was late =
afternoon and the sun  was in my eyes and the air was very bumpy. In =
addition, I was probably paying too much attention to the head =
temperatures. The purpose of the flight was to check some changes in the =
air baffling. I can assure you that never again will I land without =
being sure that I have two greens regardless of any other circumstances.

  It could have been worse, there was remarkably little damage and the =
FAA didn't get involved. A number of airport people helped me get the =
plane off of the runway and into my locked hangar as soon as possible. =
The only damage was the expected scraped belly, a little nonstructural =
damage to one wing tip, and over course, the prop.

  There has been a lot of bad mouthing of MT going on here right now, =
but my prop got abraded down to about half of it's original diameter =
without damaging either the engine or the prop hub. That is going to =
save me much money.

  The following is more speculative. I may have uncovered at least one =
cause of the down pressure switch hang up. We were having one of our =
down slope wind situations where the air temperature can jump twenty to =
thirty degrees in an hour or so, and the plane in the hangar was =
probably at least 30-35 degrees cooler than it was in flight. With that =
in mind, I tried a little experiment this morning. I went out to the =
hangar when the temperature was about 35 degrees. With the plane up on =
jacks, I retracted the gear and left it up while I warmed the hangar as =
fast as I could with a propane heater making sure that the warm air was =
circulated through the nose compartment and the cabin of the  plane. =
When the temperature in the hangar reached 80 degrees, I tried to lower =
the gear "BINGO" it was hung up. This is only one data point and it may =
not be reproducible, but it worked once for me.

  Donald Royer



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<DIV><FONT face=3DArial>THANKS for sharing Don!!!</FONT></DIV>
<DIV><FONT face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial>I have had two instances where the gear did not =
go down as=20
commanded.&nbsp;&nbsp;The first&nbsp;time it was cold (32) at take off =
and=20
warmer when I landed about 30 minutes later.&nbsp; But the 2nd time it =
was 70=20
degrees at&nbsp;take off and landing.&nbsp;As soon as I hit the reset =
button,=20
all worked as it was supposed to. </FONT></DIV>
<DIV><FONT face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial>I'm guessing that there is a piston seal(s) that =
are=20
leaking a bit and allowing pressure to bleed from the high side to the =
low=20
side.&nbsp; And the way the electro-hydraulic pump works, there is a =
pressure=20
relief valve on both the up side and down side that is supposed to =
relieve=20
excess pressure (3000 psi on high side and something lower on the low=20
side).&nbsp; This is from reading the repair manual for these =
pumps.&nbsp; On=20
marine out drive applications, they don't use any pressure switches - =
just the=20
relief valves.&nbsp;If you run the outdrive too far up or down, the pump =
keeps=20
running but excess pressure is&nbsp;relieved. I&nbsp;think the low =
pressure side=20
has something more than zero pressure on it after the gear is retracted, =
and it=20
doesn't take much of a leak from high to low side to trip the low side =
pressure=20
switch.&nbsp; I didn't put a pressure gauge port on the low side so I =
can't=20
verify this.&nbsp; Perhaps someone who has both hi and low side gauges =
installed=20
can confirm or refute these pressures.</FONT></DIV>
<DIV><FONT face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial>Not trying to preach but I try to always put my =
gear down=20
at mid field or if on a straight in&nbsp;at the initial =
approach&nbsp;fix - IAF=20
5 miles out.&nbsp; Same place EVERYTIME!!!&nbsp; Then I look at my green =
lights=20
and call&nbsp;out to myself out loud that I have two green lights on =
short=20
final.&nbsp; Now let me find some wood to knock on - here it is - =
knocking on=20
skull.&nbsp; (:^)) </FONT></DIV>
<DIV><FONT face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial>Hope you get into the air soon!!!!</FONT></DIV>
<DIV><FONT face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial>Ronnie</FONT></DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
  <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
  <DIV=20
  style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
  <A title=3Ddjroyer@earthlink.net =
href=3D"mailto:djroyer@earthlink.net">Donald=20
  Royer</A> </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dreflector@tvbf.org=20
  href=3D"mailto:reflector@tvbf.org">reflector@tvbf.org</A> </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Tuesday, April 06, 2004 =
2:07=20
  PM</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> REFLECTOR:Follow up on =
my bad=20
  landing</DIV>
  <DIV><BR></DIV>
  <P>
  <DIV>I promised more information on my bad landing last week as soon =
as I had=20
  more information. After thinking more about what happened and talking =
to=20
  several eye witnesses who between them saw all of the incident, I can =
say with=20
  some confidence exactly what happened.</DIV>
  <DIV>&nbsp;</DIV>
  <DIV>First , if was not a gear collapse, it was a gear up landing. =
What=20
  initially confused the situation was when the plane can to a stop, the =
gear=20
  was out of the gear wells and resting on the ground. In addition the =
gear=20
  switch was in the down position. However, a pilot who was out walking =
his dog=20
  at the appropriate end of the runway and who saw the final approach =
and=20
  touchdown was quite sure that the gear was in the wells at the time of =

  touchdown. That information along with the information that I reported =
before=20
  that I was distracted enough that I really could not say whether I had =
two=20
  greens or not, but that I would in all probability have seen the red =
gear=20
  unsafe light if it had been on seems to lead to one conclusion.</DIV>
  <DIV>&nbsp;</DIV>
  <DIV>The only scenario that I could come up with the fits everything =
is the=20
  following. I put the gear switch down at the appropriate time but then =
nothing=20
  happened. This possibility has been discussed here on the Reflector =
before and=20
  in fact I have installed the little circuit to bypass the down =
pressure switch=20
  to get out of this condition. Then, the shock of the landing jarred =
the system=20
  out or the hang up and the gear tried to extend as I was sliding down =
the=20
  runway.&nbsp;This conclusion is also supported by the fact that I =
heard the=20
  gear horn at about ten feet. My simultaneous reaction was to think =
that the=20
  gear warning system was malfunctioning again as it had several times =
recently,=20
  and before I got around to considering that it might be telling me the =
truth=20
  this time, I was on the ground.</DIV>
  <DIV>&nbsp;</DIV>
  <DIV>I put the cause to be a combination of a known flaw in the system =
and=20
  pilot error. I simply did not notice that the gear had not extended =
when it=20
  should have. In my defense, I was distracted at the time, it was late=20
  afternoon and the sun&nbsp; was in my eyes and the air was very bumpy. =
In=20
  addition, I was probably paying too much attention to the head =
temperatures.=20
  The purpose of the flight was to check some changes in the air =
baffling. I can=20
  assure you that never again will I land without being sure that I have =
two=20
  greens regardless of any other circumstances.</DIV>
  <DIV>&nbsp;</DIV>
  <DIV>It could have been worse, there was remarkably little damage and =
the FAA=20
  didn't get involved. A number of airport people helped me get the =
plane off of=20
  the runway and into&nbsp;my locked hangar as soon as possible. The =
only damage=20
  was the expected scraped belly, a little nonstructural damage to one =
wing tip,=20
  and over course, the prop.</DIV>
  <DIV>&nbsp;</DIV>
  <DIV>There has been a lot of bad mouthing of MT going on here right =
now, but=20
  my prop got abraded down to about half of it's original diameter =
without=20
  damaging either the engine or the prop hub. That is going to save me =
much=20
  money.</DIV>
  <DIV>&nbsp;</DIV>
  <DIV>The following is more speculative. I may have uncovered at least =
one=20
  cause of the down pressure switch hang up. We were having one of our =
down=20
  slope wind situations where the air temperature can jump twenty to =
thirty=20
  degrees in an hour or so, and the plane in the hangar was probably at =
least=20
  30-35 degrees cooler than it was in flight. With that in mind, I tried =
a=20
  little experiment this morning. I went out to the hangar when the =
temperature=20
  was about 35 degrees. With the plane up on jacks, I retracted the gear =
and=20
  left it up while I warmed the hangar as fast as I could with a propane =
heater=20
  making sure that the warm air was circulated through the nose =
compartment and=20
  the cabin of the&nbsp; plane. When the temperature in the hangar =
reached 80=20
  degrees, I tried to lower the gear "BINGO" it was hung up. This is =
only one=20
  data point and it may not be reproducible, but it worked once for =
me.</DIV>
  <DIV>&nbsp;</DIV>
  <DIV>Donald Royer</DIV>
  <DIV>&nbsp;</DIV>
  <DIV>&nbsp;</DIV>
  <P></P></BLOCKQUOTE></BODY></HTML>

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