???????? lml@lancaironline.net ????? #66641
???: Dan & Kari Olsen <olsen25@comcast.net>
???: <marv@lancaironline.net>
??: Flaps, glide ratio, RPM effects and making the runway
??: Wed, 21 Aug 2013 07:43:33 -0400
??: <lml@lancaironline.net>

LMLers,

 

During flight testing of my 320 several years ago, I collected glide ratio data for 3 different configurations as you can see below in the copy of the spreadsheet where I keep this data.

 

Config

Flaps

Gear

Prop

Decent Rate

KIAS

Glide Ratio

Cruise/low drag

up

up

low RPM

600

103

17.3

Approach/low drag

10 deg

down

low RPM

1300

92

7.1

Approach/high drag

10 deg

down

high RPM

1900

92

4.9

NOTES:

Test aircraft is Lancair 320 MKII, N320DK, owned and flown by Dan Olsen on 8/10/04

Engine is Lycoming IO-320-D1B, stock, 160hp

Prop is Hartzell HC-F2YL-8468-14D

Engine power set to idle (not completely shut off)

Empty weight

1142

Pilot

195

Fuel (36gal)

216

Baggage

20

Gross Weight

1573

Test altitude was 7500' - 9500'

Aircraft was flown with Jim Frantz's AOA Pro at the best glide AOA and KIAS was then noted

 

It is quite alarming to see the incredible difference between a clean, max glide config and a normal approach to landing config.  Glide ratio goes from 17:1 down to 5:1.  I remember speaking with Orin Riddel at the Lancair factory years ago and him describing that if you were on downwind, abeam the numbers, and your engine quit and you left it in the high-drag congif, you will not make the runway.  First reaction should be to immediately retract the gear, low RPM on the prop and get the flaps up.

 

I practice this scenario regularly and I can always make the runway with the main issue typically being that I land long and have to turn up the RPM to add drag on short final:

·         Fly normal downwind

·         Chop the throttle to dead idle on downwind

·         Low RPM (coarse pitch)

·         Gear and flaps up

·         Pitch for best L/D on the AOA

·         Fly the pattern (tighter than normal)

·         On short final when runway is assured, drop the gear and 10deg flaps

·         Add flaps and increase RPM, as necessary, to avoid landing dangerously long

 

I encourage all Lancair drivers to get some experience with your plane in the various drag scenarios with the engine at idle, especially the dramatic difference that flat vs. coarse pitch on your prop makes.  There is nothing like feeling it for real to teach you some of the “muscle memory” needed to react in a pinch.

 

Upon departing OSH a few weeks ago, I wanted to fly across Lake Michigan to visit my daughter.  Going around is very long and going over is very scary J  So, I was able to take the knowledge from actual glide testing of my 320 to create the following table to show how high above the water I need to be in order to glide to the shore in the case of engine failure at the middle of the lake.  The area of the lake I went across was about 60nm across, so 30nm from center to shore.

 

Lancair 320

N320DK

Glide Ratio

17

15

12

10

8

7

5

Distance to Glide (nm)

50

    17,871

    20,253

    25,317

    30,380

    37,975

    43,400

    60,760

45

    16,084

    18,228

    22,785

    27,342

    34,178

    39,060

    54,684

40

    14,296

    16,203

    20,253

    24,304

    30,380

    34,720

    48,608

35

    12,509

    14,177

    17,722

    21,266

    26,583

    30,380

    42,532

30

    10,722

    12,152

    15,190

    18,228

    22,785

    26,040

    36,456

25

     8,935

    10,127

    12,658

    15,190

    18,988

    21,700

    30,380

20

     7,148

     8,101

    10,127

    12,152

    15,190

    17,360

    24,304

15

     5,361

     6,076

     7,595

     9,114

    11,393

    13,020

    18,228

10

     3,574

     4,051

     5,063

     6,076

     7,595

     8,680

    12,152

5

     1,787

     2,025

     2,532

     3,038

     3,798

     4,340

     6,076

1

        357

        405

        506

        608

        760

        868

     1,215

Clean
Low RPM

Landing
Low RPM

Landing
High RPM

 

My table shows about 12,500’ above the water (approx. 13,500’ MSL) would get me to the shore (to be conservative I used a 15:1 glide ratio even though my testing showed 17:1 because the engine was still producing minimal power during the test).  So, with approved floatation gear donned, we charged across at 15,500’, giving us a good 5nm of buffer to account for extra weight and other fudge factors.

 

I hope this data is helpful to some of you and encouraging to others to go do this testing and practice engine-out procedures in your Lancair.

 

Regards,

 

Dan Olsen

N320DK – 750 hrs

IV-P in gestation

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