Colt Glide speed?

[Will K]

What's your best glide speed? I'm still getting used to our Colt and went out today with my grown son to see if we could determine best glide speed. Here is what we were able to determine on todays flight.

IAS was used:
75mph = 800 fpm descent, 733 feet lost in a nautical mile.
70 mph = 700 fpm descent, 700 feet lost in a nautical mile.
65 mph = 650 fpm descent, 688 feet lost in a nautical mile.

All tests were done in two opposing directions at roughly 3500 MSL and we were roughly 160 lbs below max gross weight. We only tested those three speeds today as we had to get back home.

 

[Subsonic]

What's your best glide speed? I'm still getting used to our Colt and went out today with my grown son to see if we could determine best glide speed. Here is what we were able to determine on todays flight.

IAS was used:
75mph = 800 fpm descent, 733 feet lost in a nautical mile.
70 mph = 700 fpm descent, 700 feet lost in a nautical mile.
65 mph = 650 fpm descent, 688 feet lost in a nautical mile.

All tests were done in two opposing directions at roughly 3500 MSL and we were roughly 160 lbs below max gross weight. We only tested those three speeds today as we had to get back home.

I'm going to have to check that out in my Tri-Pacer. I don't know where I heard it, but I thought my best glide was around 80mph. That's what I've used in engine out drills. But your data suggests it might be a much lower speed. I just checked my Owner's Manual and can't find that spec listed. Was your throttle backed all the way out?

 

[N2709P]

Some basic ideas from the FAA regarding how to find best glide for your aircraft.

~~Marsha

 

[Will K]

I'm going to have to check that out in my Tri-Pacer. I don't know where I heard it, but I thought my best glide was around 80mph. That's what I've used in engine out drills. But your data suggests it might be a much lower speed. I just checked my Owner's Manual and can't find that spec listed. Was your throttle backed all the way out?

That is correct. Engine at full idle. We decided to do this as the Owners Manual for the Colt also does not list a best glide speed and most of the research I've done shows typical best glide speed is somewhere between Vx and Vy. The manual shows Vx as 60 and Vy as 76 which is why I focused on those speeds.

We climbed to 3900 ft MSL, pulled power and would trim for the desired speed and my focus became airspeed and heading control. At 3700 ft, my son started the timer for 30 seconds and he would verbally start a countdown with 5 seconds remaining so I could note the indicated altitude. I want to go back up soon to ensure I can duplicate the numbers on another day as well as test out a flare if I'm already slowed down to 65mph, or whatever speed we determine to be best glide.

When I bought the Colt the previous owner advised for 80 on final which has worked well for standard landings.

 

[at7615]

I'm going to have to check that out in my Tri-Pacer. I don't know where I heard it, but I thought my best glide was around 80mph. That's what I've used in engine out drills. But your data suggests it might be a much lower speed. I just checked my Owner's Manual and can't find that spec listed. Was your throttle backed all the way out?

Greetings, any more data?

 

[dgapilot]

Don’t forget that aircraft weight has a large impact on those speeds. The TriPacer best glide is based on 2000 lbs gross weight. The Colt would be based on 1650 lbs gross weight so the “best glide” will be at a slower speed.

Best glide speed is really a useless concept as it depends on the air mass you are traveling through. Anyone that has flown gliders would use the term “speed to fly” based on the drag polar, the McReady rating of the airmass and the relative lifting or sinking in the immediate airmass you are traveling through. If you are in lift you slow down to just about stall speed, if you are in sink, you speed up to penetrate through the sink.

When these airplanes were made there was very little required performance data, best glide wasn’t even considered. If you are worried about having numbers for your check ride, the DPE can’t ask for any data that wasn’t provided by the manufacturer. They can’t even really ask for stuff in the POH as that is not a required document. The only thing that is fair game is what is in the Flight Manual as that is the required document that has to be in the aircraft for all operations.


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[Subsonic]

Don’t forget that aircraft weight has a large impact on those speeds. The TriPacer best glide is based on 2000 lbs gross weight. The Colt would be based on 1650 lbs gross weight so the “best glide” will be at a slower speed.

Best glide speed is really a useless concept as it depends on the air mass you are traveling through. Anyone that has flown gliders would use the term “speed to fly” based on the drag polar, the McReady rating of the airmass and the relative lifting or sinking in the immediate airmass you are traveling through. If you are in lift you slow down to just about stall speed, if you are in sink, you speed up to penetrate through the sink.

When these airplanes were made there was very little required performance data, best glide wasn’t even considered. If you are worried about having numbers for your check ride, the DPE can’t ask for any data that wasn’t provided by the manufacturer. They can’t even really ask for stuff in the POH as that is not a required document. The only thing that is fair game is what is in the Flight Manual as that is the required document that has to be in the aircraft for all operations.
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Just wanted to know truth in the universe. Interesting that you know what a DPE can ask. Speaks to a depth of knowledge I don't have. Thanks for your insight.

I have a '56 TP and routinely fly with just my 155 pound body and camping gear/or regular luggage, full gas, some tools/oil/tie down's, airplane stuff, etc. Less than full gross.

The ASI is so coarse in my experience that plus or minus 5 mph is almost in the noise. I just go by feel.

Aside comment regarding glide "feel": I have 620 skydives and ram air parachute glide ratios are around 3 or 4.5:1. They lie about reality so don't research it unless you really jump out of airplanes.

In a fixed wing airplane, I try to keep that feeling of max lift, like I'm sitting on an egg, and watch my airspeed and vertical speed and try to get to a best glide. I think it's around 75 or 77mph for me in my TP set up, at probably around a total weight between 1600 and 1750 pounds solo. Just my input.

-Subsonic

 

[Kelliots]

When my Colt's engine quits, I'm gonna fly 70 MPH and head for the nearest field I can find, keeping an eye out for power lines.....