Lift Reserve Indicator

[Rynoth]

Here's my test plan. Take off and get at least 3000 AGL. Set my altitude bug to my altitude (virtual field elevation). Start a typical Vy climb simulating a power climb. 300 ft above the bug, pull the power (simulate engine failure) and execute a 180 turn keeping the plane in Vy using the LRI. How did it work? Low or high? Now do it again. This time increasing my turn rate to the point of stall/spin. Eventually spinning it. Repeat until I can just do the 180 turn without spinning. That will tell me the minimum altitude required to execute a 180 turn without an engine and without a spin.

This would be a perfect test with an LRI as well. LRI shouldn't lose any accuracy at higher airspeeds/accelerated turning stalls (though the reference point for the stall may shift.) With an LRI you could do this maneuver, and note the position of the LRI when the stall occurs in the steep-banked turn. Now you have an LRI reference that can tell you just how hard to pull to execute a safe, aggressive turnback.

We practice this maneuver in the PC12 (in the simulator) and use Angle of attack exclusively for the turn, it allows you to pull the maximum available g's for the fastest turnaround time. It usually involves dropping the nose a LOT in order to keep the airspeed up. As soon as the turn is complete, you ride the excess airspeed in a balloon upwards, putting you in a great position to dump the gear/flaps and land. We use a 45 degree bank, although we demonstrated that up to a 60 degree bank can actually get you the best results... but 60 degrees is an unusual maneuver and more likely to screw up. 1000' AGL is our turnaround minimum.

Just remember, if you're executing an aggressive turnback, best-glide speed isn't going to cut it. You need more speed to pull the plane through the steep bank. This means dropping the nose, sometimes by a lot. Once you're level, ride the extra airspeed back to best glide if you need to.

[Bryan Cotton]

Turn rate is proportional to the square of airspeed. Good to be as slow and steep as possible - without stalling of course. I think in a light aircraft I would get turned around as fast as possible then go for the extra airspeed I would need in the flare. The problem with going too fast for your polar is you end up with a lot of drag at those higher speeds, which means you end the turn with less altitude, even after converting excess speed to height. I bet the PC12 has a much higher Vy than the lighter stuff.

[radfordc]

Ryan nailed it. When I did it I chopped power in a climb, popped the stick forward and hard over into a 45 degree bank and then pulled until I felt the onset of a stall. Rudder to keep the ball centered and let the nose fall through to keep the airspeed safe.

[Rynoth]

Turn rate is proportional to the square of airspeed. Good to be as slow and steep as possible - without stalling of course. .

Precisely. Which is why AOA or LRI is helpful in getting you to that steep, slow bank without stalling. I'm not saying to dive for the dirt, I'm saying extra airspeed will allow you a steeper bank, and that extra airspeed is likely above best glide speed. Also, the induced drag in the steep turn is going to bleed speed, so the pitch has to be quite low (which is probably the hardest part, pointing the nose towards the ground.) It's about spending as little time/distance/altitude going in any direction that is NOT the direction of the airport.

The other tip in such a maneuver is not to over-turn to try to line up with the runway, right away. Just aim directly at the approach end of the runway and make your adjustments from there.

If you're going to impact terrain, here's you're mantra, remember it forever: "Wings level, don't stall". Do that, your chances to walk away go up by... a lot.

PC12 Vx/Vy/Best glide are all between 110-120 kts. Full flap stall speed is 64 at 10,000 lbs. Love that plane.

[radfordc]

If you're going to impact terrain, here's you're mantra, remember it forever: "Wings level, don't stall". Do that, your chances to walk away go up by... a lot.

Bob Hoover also said, "Fly the plane as far into the crash as possible".

[Darick]

Ryan,
I was on your website and see I have the same lift reserve indicator. In a week or two I'll be at the point of installing it and wondered if you any words of wisdom/tips on your installation? ...left wing, right wing, placement from wing tip, etc?
Thanks for any info.

[Rynoth]

Ryan,
I was on your website and see I have the same lift reserve indicator. In a week or two I'll be at the point of installing it and wondered if you any words of wisdom/tips on your installation? ...left wing, right wing, placement from wing tip, etc?
Thanks for any info.

Hi Darick,

I placed it in the identical location as the pitot tube in the plans, but on the left wing. I believe it's just inside the 5th fwd wing rib, as close to the spar as the installation will allow.

Pictures and details of my installation here, if you didn't already see it.

http://www.rynoth.com/wordpress/waiex/2 ... indicator/

[MJHall]

Hi guys, I've been lurking here a while, so first post. Not building, but gathering information. The LRI instrument is interesting. For the $$, I would say it is attractive because it is a completely redundant/independant source of very valuable information, especially if you install in the opposite wing as Rynoth suggests. I have not used this instrument, and suppose it would take some getting used to for us "old guys", but is probably worth it.

[daleandee]

I have not used this instrument, and suppose it would take some getting used to for us "old guys", but is probably worth it.

Hi Mike,

Pretty easy to install and use. Here are a few links if you haven't already seen them:

http://sonexbuilders.net/viewtopic.php?f=21&t=714#p5120

Dale
N319WF

[fastj22]

I really used my LRI today.
Few to Leadville, CO with my wife for the Colorado Pilots Association pancake flyin. Field elevation of 9930 ft. DA indicated 12,200ft on my EFIS.
Landing was a non-issue. But takeoff was different. 6000ft of runway, probably used 4000ft of it before my LRI said I had enough lift. Then just kept in the white region trying to climb out. I didn't once look at airspeed, just concentrated on keeping the needle between Vy and Vx. On my LRI, Vx is the line between red and white. Vy is white to green. Eventually out climbed and was faster than the C182 ahead of me. Once I got 1000ft AGL, pushed the nose down, the LRI went into the green and we started to scream. Climbed to 12,500ft and heading over the ridge.