Backup for dropping the gear

In a previous article, Kyler Laird said:
Is there a placard that says "Do not lose engine power in excess of max.
gear extension speed."?

There would be no need for such a placard.

Yeah, it looks like it would need to be "Do not leak hydraulic fluid in
excess of max. gear extension speed."

On the Lance (which is the only plane I have any experience with), even if
you lost hydraulic fluid, air pressure would hold the gear up against the
springs until you dropped down to max gear extension speed. I suspect
you'd get a bit more drag from the gear drooping slightly into the
airstream, though.



--
Paul Tomblin http://xcski.com/blogs/pt/
You can be jailed for lying about being good in bed.
-- Lionel, paraphrasing the Criminal Code of Canada, 159(3)(b)(i)

Paul Tomblin wrote:
On the Lance (which is the only plane I have any experience with), even if
you lost hydraulic fluid, air pressure would hold the gear up against the
springs until you dropped down to max gear extension speed. I suspect
you'd get a bit more drag from the gear drooping slightly into the
airstream, though.

Okay Paul, I have to ask you to explain those two statements.

In a previous article, john smith said:
Paul Tomblin wrote:
On the Lance (which is the only plane I have any experience with), even if
you lost hydraulic fluid, air pressure would hold the gear up against the
springs until you dropped down to max gear extension speed. I suspect
you'd get a bit more drag from the gear drooping slightly into the
airstream, though.

Okay Paul, I have to ask you to explain those two statements.

What don't you understand? In the Lance, the hydraulic system is there to
raise the gear. Besides manually lowering the gear, there is an automatic
gear extension system and a manual emergency gear extension system.

If you activate the manual emergency gear extension system, springs and
gravity bring the gear down - I'm not entirely clear if hydraulic pressure
helps bring them down if you use the normal gear extension. The
description of the emergency gear extension system in the POH says that
the speed the gear will come down is lower if the plane is developing
power because the prop slipstream holds it up.

I'm told (I haven't verified it yet) that if you activate the emergency
gear extension when you're above max gear speed, the gear won't come down,
but will come down slightly into the airstream developing drag.

--
Paul Tomblin http://xcski.com/blogs/pt/
"The way I see it, unless we each conform, unless we obey orders, unless
we follow our leaders blindly, there is no possible way we can remain
free." - John Ashcroft^W^WFrank Burns

Paul Tomblin wrote:
In a previous article, john smith said:

Paul Tomblin wrote:

On the Lance (which is the only plane I have any experience with), even if
you lost hydraulic fluid, air pressure would hold the gear up against the
springs until you dropped down to max gear extension speed. I suspect
you'd get a bit more drag from the gear drooping slightly into the
airstream, though.

Okay Paul, I have to ask you to explain those two statements.


What don't you understand? In the Lance, the hydraulic system is there to
raise the gear. Besides manually lowering the gear, there is an automatic
gear extension system and a manual emergency gear extension system.

If you activate the manual emergency gear extension system, springs and
gravity bring the gear down - I'm not entirely clear if hydraulic pressure
helps bring them down if you use the normal gear extension. The
description of the emergency gear extension system in the POH says that
the speed the gear will come down is lower if the plane is developing
power because the prop slipstream holds it up.

I'm told (I haven't verified it yet) that if you activate the emergency
gear extension when you're above max gear speed, the gear won't come down,
but will come down slightly into the airstream developing drag.

I do not believe the air flowing under the wings will hold the gear up.
If the hydraulic pressure is released, the gear will come down.
If you are flying fast, the air may grab the gear doors and possibly rip
them off or otherwise torque/twist the gear (whichever comes first).
Look up stories about the P-51B (or C?) and the redesign of the gear
uplock. Granted, you do not have the Mustang's cruise speed, but the
principle is the same if you exceed Vge/Vgo.

The override prevents the gear from automatically deploying.
You still have to push the lever to release the hydraulic pressure to
enable the gear to drop. The POH further says to kick the rudder right
and left to create a sideward airload on the gear to lock it into
position. In some cases, you must stall the aircraft to get the nosegear
to lock by penduluming forward as the nose drops and airload is decreased.

(Paul Tomblin) writes:

Yeah, it looks like it would need to be "Do not leak hydraulic fluid in
excess of max. gear extension speed."

On the Lance (which is the only plane I have any experience with), even if
you lost hydraulic fluid, air pressure would hold the gear up against the
springs until you dropped down to max gear extension speed. I suspect
you'd get a bit more drag from the gear drooping slightly into the
airstream, though.

Now *that* makes sense. I caught that there was a sensor connected to
the pitot tube that interacted with the gear, but it's clever to use
airflow to keep it from dropping on its own too soon. Thank you for
explaining it.

(BTW, some of my confusion with hydraulics is because of my background
with farm machinery where the oil flows through the valve when "off" -
not because the explanations in this thread were misleading.)

--kyler