Hi Doug,
We installed Adam’s closing inboard gear door system for general takeoff & landing performance and handling improvements and not really for improved
engine out gear down glide. As you said, in an engine out emergency, the gear are likely coming down just before landing.
I don’t know if by now Adam has put together any numbers on the benefits of closing the inboard gear doors when the gear are down. We added the system
years ago based on these likely benefits:
·
Better Lift/Drag ratio in landing and takeoff configuration (little wings, big openings in bottom)
·
Reduced gust disturbance effects in gear down config
·
Reduced wear on inboard gear doors (noticed they take a bit of punishment even when people are taxiing, from the propeller slip stream)
·
Reduced contamination thrown up in wheel wells
Won’t know if the system is worth the added complexity until flying. Adam has one of the more elegant solutions, though, with a hydraulics manifold
and cross over valve to handle the sequencing. He also reports that it’s a lot quieter in the cockpit with the gear down with the inboard doors closed.
On the hydraulic system, from reading Chris Zavatson’s excellent report on the system, Legacy airplanes have various configurations of the pump depending
on when the kit was shipped. We have a pre-2005 kit which is a hybrid between what was used in 320/360’s and the Legacy’s baseline system today. I think William Ford has the same configuration and so what he’s experiencing is likely what we’ll experience.
Do you have a post-2005 Legacy kit? I’m probably going to just change out the spool for a symmetric one based on Chris’ recommendation.
Thanks. Appreciate your thoughts on all this.
Valin
From: Lancair Mailing List [mailto:lml@lancaironline.net]
On Behalf Of Dennis Johnson
Sent: Wednesday, April 23, 2014 10:18 AM
To: lml@lancaironline.net
Subject: [LML] Re: Hartzell Prop Governor Low RPM Capability
I'm not sure why you're concerned about the extra drag from the main landing gear doors. When I practice simulated engine out landings, I don't lower the gear until it's
clear that I'm going to land too long if I don't do something to slow down. If I had a real engine failure and wasn't going to make it to a runway, I'd probably leave the gear up.
Regarding the need to cycle the dump valve to get the landing gear up or down, in 700 hours in my Legacy, I've never had a problem that required opening the dump valve.
My guess is that it's a rare condition, possibly limited to a small number of Legacies, most likely due to a problem with the hydraulic power pack. Based on my experience, I wouldn't add more time, money, and parts count to solve a problem that's unlikely
and, if it does occur, has a simple immediate fix.
----- Original Message -----
Sent: Tuesday, April 22, 2014 12:03 PM
Subject: [LML] Re: Hartzell Prop Governor Low RPM Capability
Thanks John. Makes it clear why one of the Legacy instructors was quoted as saying, “With the engine out, the Legacy comes down like a greased Buick”
– I guess specifically talking about with the gear down.
We have Adam Molny’s closing inboard landing gear door system which should help with the gear down drag a lot. Adam, if you see this, do you have engine
off sink rate numbers with your gear down and inboard doors closed you can share for comparison?
Thanks,
Valin Thorn
Legacy Project
Boulder, Colorado