Engine-out Flight Testing

[Joe Dubner]

I did some engine-out flight testing the other day and thought I'd share my results FWIW.  My airplane is an O235-L2C Long-EZ with high-compression pistons, a Hertzler propeller, wheel pants, and gear leg fairings.  Gross weight was about 1200 pounds.  I climbed to 14,500 and stayed within about 10 miles of the airport (1424 MSL).

With the ignition and fuel off, I found that the prop would windmill down to 70KIAS.  As I lowered the nose, it would "tick over" occasionally at 85 - 90 KIAS but not enough to start the engine.  It was necessary to attain 110 KIAS before the engine started.  This surprised me as I had been led to believe by the pundits that it would take considerably more airspeed.

With a windmilling prop the rate of descent was 800 - 900 fpm at about 80 KIAS.  After I stopped the prop and set up a a 75 KIAS glide, the rate of descent was slightly less at 700 - 800 fpm.  The pitch attitude was a mild 3 - 5 degrees nose low.  With full aft stick the airplane indicated 51 KIAS and about 500 feet per minute rate of descent -- very similar to what I've seen at idle thrust.

Regrettably, I didn't take the time at altitude to lower the nosegear and landing brake to note the additional descent rate.  And when I lowered them for the landing, I was too busy to take notes  :-)  All in all, I spent about 15 minutes from engine shutdown to touchdown which equates to an 866 fpm average descent rate and agrees with what I saw on the VSI.  My groundtrack covered about 25 NM, although I could easily have stretched that if I had maintained the optimum airspeed and not turned so much.

Next time (although I'm not sure there will be a "next time") I would use a voice recorder to log airspeeds, rates of descent, etc.  Writing on my clipboard was a poor way to go.  Also, I'd probably restart the engine at low key and use idle power for the remainder; the performance difference isn't worth the additional risk IMO.

[Waiter]

EXCELLENT DATA. I don't recall my exact numbers but I seem to remember the restarting for my O-320 was higher, i.e. 140 kts.

Next time (although I'm not sure there will be a "next time") I would use a voice recorder to log airspeeds, rates of descent, etc. Writing on my clipboard was a poor way to go. Also, I'd probably restart the engine at low key and use idle power for the remainder; the performance difference isn't worth the additional risk IMO

If you have a laptop, try using my recorder. It will record a DYNON EFIS, Dynon EMS or Grand Rapids EMS, and GPS, All at the same time, or seperatly.  I.e. if you only have a GPS, then it will record the data from that, once per second.  The recorded file can then be viewed with any text editor, or loaded into any spreadsheet program.

No More kneeboards, or missed data

www.iflyez.com

Waiter

[Drew]

Engine (O235, O320, etc), compression, and prop pitch/diameter should all effect your engine "relight" speed.  Those with high compression, big engines, and cruise props should have a harder time than that same engine with a climb prop.

And you dead sticked it too?  More guts than me.  Glider pilots never seem to concerned that they don't have an engine.  

[Jack]

I  All in all, I spent about 15 minutes from engine shutdown to touchdown which equates to an 866 fpm average descent rate and agrees with what I saw on the VSI.  My groundtrack covered about 25 NM, although I could easily have .

I posted last year or before engine out data flights. Except I started at 10,000' and relit at 5,000'.  You will find your VSI decreases as you descend for the lower altitudes.  I just held her at 70KIAS and came on down.

It took 110KIAS to relight my engine also.  I did it with and without the prop stopped. With the prop stopped you decreased VSI by 15% or so.

If somebody else is planning on trying glide distance.  Do it over a big airport and be prepared for a relight.  I used a fairly hot day and the engine didn't cool down too much. Still I cranked her at idle and left it there for a couple of mins.

It gets real quiet up there and having a camcorder or other recording device helps.

Cheers;

Jack