Glide ratio for a Lance

[TMetzinger]

I'm going to be flying a 1978 Turbo Lance next week over water (WAAY out of gliding distance to land) and can't find a gliding distance chart in the AFM.

Anybody have any good info on how many miles per 1000 feet I can glide at best glide of 92 KIAS?

Yes, we have a raft, and a PLB, and since we're doing data collection for a rocket launch, we'll be in constant contact with folks. Just looking to guestimate the potential for gliding.

 

[EdFred]

RG or FG? laden or unladen?

 

[Greg Bockelman]

Brick?

 

[jsstevens]

Brick?

I think it's probably aluminum siding...:wink2:

 

[COFlyBoy]

Here are the numbers for a '66 Cherokee 6

Best glide speed: 100mph, 87 kts, 1.45 nm/minute
Descent Rate at best glide (engine running throttle closed): 1250 fpm, 1.25 kfpm

Gives a disturbing glide slope of: 1.16 nm/1000'

 

[Ted]

Having no useful data, I'll second Greg:

Out of curiosity, where will you be flying?

 

[vontresc]

Here are the numbers for a '66 Cherokee 6

Best glide speed: 100mph, 87 kts, 1.45 nm/minute
Descent Rate at best glide (engine running throttle closed): 1250 fpm, 1.25 kfpm

Give a disturbing glide slope of: 1.16 nm/1000'

That's roughly a 7:1 glide ratio. Still better than the Space Shuttle (4.5:1), and a Flying Squirrel (1.98:1).

 

[tonycondon]

7:1 is about what i was getting on my flight last weekend diving into that wind. ugh.

 

[Richard]

RG or FG? laden or unladen?

European or African?

 

[tonycondon]

hey you guys should know that glide ratio is not affected by weight!

 

[TMetzinger]

Having no useful data, I'll second Greg:

Out of curiosity, where will you be flying?

Off the Atlantic Coast from Wallops Island, in W-386.

I was pleasantly surprised to find a 4 person raft and PLB will only cost $51 per day. From a knowledgable source I've been told a 7.5 ratio, which I'm going to take down to 6:1 to make up for plane condition (the sensor antennae doubtless add drag) and for my less-than-test-pilot abilities. But at least I can guestimate feet dry at 10 NM or so

 

[Sam D]

I'm going to be flying a 1978 Turbo Lance next week over water (WAAY out of gliding distance to land) and can't find a gliding distance chart in the AFM.

Anybody have any good info on how many miles per 1000 feet I can glide at best glide of 92 KIAS?

Yes, we have a raft, and a PLB, and since we're doing data collection for a rocket launch, we'll be in constant contact with folks. Just looking to guestimate the potential for gliding.

For 76 NA Lance, it's 1.6 miles for each 1000 feet (3.13 of POH -- Power Off Landing). Best glide is also 92 kts.

 

[Henning]

Off the Atlantic Coast from Wallops Island, in W-386.

I was pleasantly surprised to find a 4 person raft and PLB will only cost $51 per day. From a knowledgable source I've been told a 7.5 ratio, which I'm going to take down to 6:1 to make up for plane condition (the sensor antennae doubtless add drag) and for my less-than-test-pilot abilities. But at least I can guestimate feet dry at 10 NM or so

7.5 is pretty correct, as for 10NM, that would depend on the winds.

 

[AdamZ]

I flew a 76 lance for a short time ( Straight Tail) and it was indeed a rock.

 

[Ted]

Off the Atlantic Coast from Wallops Island, in W-386.

Yeah, that does give you some opportunity for flying out of gliding range. Sounds like fun! Funny thing - after all my Gulf flying in July, flying over land again felt odd. I've since gotten used to it.

I was pleasantly surprised to find a 4 person raft and PLB will only cost $51 per day. From a knowledgable source I've been told a 7.5 ratio, which I'm going to take down to 6:1 to make up for plane condition (the sensor antennae doubtless add drag) and for my less-than-test-pilot abilities. But at least I can guestimate feet dry at 10 NM or so

I don't know, some of the test pilots I've met aren't anything to write home about.

 

[EdFred]

I would put the glide ratio of a Lance at 0:1. Of course that would be a Lance Fisher, or Lance Flynn.

 

[Baron2PG]

Put 500+ hours in a 1978 Turbo Lance - The brick comments would be funny if they weren't true. The following is from my emergency sheet that was the cover of my kneeboard.

SPEEDS​

Vmg Max Glide 92 kias​

(1.2 nm/1000’)​

Vcc Cruise Climb 105 kias​

Vx Best Rate 95 kias​

Vy Best Angle 82 kias

Va Maneuvering 132 kias​

Vfe Flap Extend 109 kias​

Vso Stall Dirty 52 kias​

Vs Stall Clean 57 kias​

Vne Never Exceed 191 kias​

Vno Max Cruise 150 kias​

Vge Gear Extend 129 kias​

​

WEIGHT​

3600 lbs Max Gross Weight​

1252 lbs Usable – Usable Fuel (6lb/Gallon)​

688 lbs Usable w/ Full Tanks​

Ref W&B Sheet​

PA32RT-300T (P32T)​

S/N 32R-7887157​

 

[Ark235B]

I don't think they glides as bad as a brick.

 

[gismo]

I would put the glide ratio of a Lance at 0:1. Of course that would be a Lance Fisher, or Lance Flynn.

I've managed close to a 1:1 "glide" ratio on some waterski jump falls. Touchdown wasn't exactly a greaser either.

 

[EdFred]

I've managed close to a 1:1 "glide" ratio on some waterski jump falls. Touchdown wasn't exactly a greaser either.

More like a series of tumbling ground loops?

 

[gismo]

Put 500+ hours in a 1978 Turbo Lance - The brick comments would be funny if they weren't true. The following is from my emergency sheet that was the cover of my kneeboard.

SPEEDS
Vmg Max Glide 92 kias
(1.2 nm/1000’)​

​

1.2 nm / 1000 ft altitude loss sounds about right although I don't know if that's with the prop control set for cruise RPM or pulled all the way out which generally increases gliding range by 20-30%. Also it's important to remember that the speed for best glide range decreases with the square root of the weight and varies considerably with wind.

IIRC the ROT is to decrease your airspeed by 10% of a tailwind but never go slower than min sink speed and add 15% of a headwind.

 

[tonycondon]

[/CENTER]

1.2 nm / 1000 ft altitude loss sounds about right although I don't know if that's with the prop control set for cruise RPM or pulled all the way out which generally increases gliding range by 20-30%. Also it's important to remember that the speed for best glide range decreases with the square root of the weight and varies considerably with wind.

IIRC the ROT is to decrease your airspeed by 10% of a tailwind but never go slower than min sink speed and add 15% of a headwind.

I analyzed the polar on our clubs Blanik trainer once and decided about 30% of the headwind was best for it. I think its more for lower performance gliders (like airplanes with failed engines). In the Schweizer 2-22 and 2-33 tanks and in my Cherokee II I usually add 50% of the headwind. Of course I also do my best not to glide into the wind in those too.

 

[bbchien]

In a Lance figure 1000 fpm descent with power off at Vglide; figure the effects of wind based on the resultant time to ground.....

 

[Henning]

[/CENTER]

1.2 nm / 1000 ft altitude loss sounds about right although I don't know if that's with the prop control set for cruise RPM or pulled all the way out which generally increases gliding range by 20-30%. Also it's important to remember that the speed for best glide range decreases with the square root of the weight and varies considerably with wind.

IIRC the ROT is to decrease your airspeed by 10% of a tailwind but never go slower than min sink speed and add 15% of a headwind.

6000*1.2=7200= 7.2:1, sounds right for max gross, but remember, rarely will you be at max gross, especially considering the most common reason for the exercise is that you don't have fuel in the tanks.

As for pulling back the prop govenor, I haven't seen it make a difference. I've heard a ton of claims, but I haven't seen it work. How much effect does that handle have at idle? Ain't no 20-30% glides worth. You barely get that with a stopped prop, and the only way you can beat that is in feather. Those are not variable pitch props, those are constant speed and you are controlling a governor that controls upper RPM, the throttle is what controls the lower RPM. Once you drop below 1600 rpm with a CS prop, the governor has typically reached the bottom of its range and the blades will sit at fine pitch until power is added and RPMs increased. Windmilling props typically turn 1200rpm or less so adjusting the governor does basically nothing. Which brings me to a long long long standing pet peeve. Fast/heavy SE aircraft should have a feathering CS prop if they are going to have a CS prop. Use rotating engine or accumulator oil pressure to drive the props against the spring and past a detent when you have exhausted your options and are now making the best out of a not so good situation. It defaults fine and gets driven into feather detent once committed.

 

[tonycondon]

why would the glide ratio change if you aren't at max gross?

 

[Henning]

hey you guys should know that glide ratio is not affected by weight!

No, but glide speed is.

 

[gismo]

As for pulling back the prop govenor, I haven't seen it make a difference. I've heard a ton of claims, but I haven't seen it work. How much effect does that handle have at idle? Ain't no 20-30% glides worth. You barely get that with a stopped prop, and the only way you can beat that is in feather. Those are not variable pitch props, those are constant speed and you are controlling a governor that controls upper RPM, the throttle is what controls the lower RPM. Once you drop below 1600 rpm with a CS prop, the governor has typically reached the bottom of its range and the blades will sit at fine pitch until power is added and RPMs increased. Windmilling props typically turn 1200rpm or less so adjusting the governor does basically nothing. Which brings me to a long long long standing pet peeve.

I suppose it depends on the airplane's best glide speed but in a Bonanza the effect is substantial. There the speed is 100-110 KIAS and with a windmilling prop the RPM will go from around 2200 down to something like 1000 when you pull the control all the way out. When the prop control is left at a normal cruise setting (e.g. 2500) an engine failure will put the prop on the low pitch stops with the governor trying to keep the RPM at 2500. Most singles with CS props are set up so the governor can reach near idle speeds so you can do a "prop check" at a reasonably low RPM. A fast airplane also must have the high pitch stops set at a pretty big angle, not feathered by any means but way closer than the low pitch stops so it's unlikely that pitch limits will be reached with the governor set for min RPM. In any case if you simply figure the extra horsepower required to spin the engine above 2000 RPM vs 1000 RPM (don't forget to include prop efficiency) and translate that HP into FPM at your weight (1HP= 33,000 Ftlbs/min) you can see that the approximately 20 HP difference would yield about 250 FPM less descent rate.

 

[TMetzinger]

As for pulling back the prop govenor, I haven't seen it make a difference. .

I did experiments in the Trinidad, and with a windmilling WORKING engine it makes a difference, since there's still oil pressure to force the blades to coarse pitch.

In the event of a catastrophic engine failure due to internal mechanical problems I'd expect the engine to seize and the prop to be fine. Not sure what that drag is like, but I don't think I'll like it.

 

[tonycondon]

if the engine siezes wouldnt the prop be stopped? assuming the prop is still connected solidly to said engine.

 

[Henning]

if the engine siezes wouldnt the prop be stopped? assuming the prop is still connected solidly to said engine.

Yep, however, considering fuel exhaustion is the most common cause of engine failure, the prop won't necessarily stop.

 

[TMetzinger]

if the engine siezes wouldnt the prop be stopped? assuming the prop is still connected solidly to said engine.

So, for the aerodynamicists - how does the drag of a stopped prop (siezed) compare to a windmilling prop?

Assume a fixed-pitch prop for simplicity.

 

[tonycondon]

i was always told in multi training that a windmilling prop has the same drag as a flat plate. based on what it feels like when you feather one, i believe it.

 

[jesse]

So, for the aerodynamicists - how does the drag of a stopped prop (siezed) compare to a windmilling prop?

Assume a fixed-pitch prop for simplicity.

I'm no aero engineer - but when the prop stops - you glide a hell of a lot better. It takes energy to spin that thing around.

 

[TMetzinger]

i was always told in multi training that a windmilling prop has the same drag as a flat plate. based on what it feels like when you feather one, i believe it.

I do too... but what's the drag of a stopped but NOT feathered prop?

 

[jesse]

I do too... but what's the drag of a stopped but NOT feathered prop?

A lot of variables, no definite answer, but less than a windmilling not feathered prop.

 

[John Collins]

I don't have any facts to back this up, but I believe that a stopped prop is much closer to a feathered prop than to a windmilling prop. If the prop is turning, it is extracting energy from the air to overcome the compression strokes in the engine.

My engine idles at 600 RPM on the ground, but if I pull the throttle to idle in the air, it turns anywhere from 1800 RPM down to 1100 RPM, depending on the position of the prop control. So another way of looking at it is the same as adding 500 to 1200 revolutions per minute to the ground idle. It takes a fair amount of energy for me to turn my engine over manually at one or two RPM, so you can imagine what it takes to add 500 to 1200 RPM. If it stops, I have just the flat plate drag of the prop to consider.

My Bonanza has a glide ratio slightly better than 10 to 1 according to the POH, but I experience closer to 12 to 1 with the prop at the full rear stop. If the prop were stopped, I would not at all be surprised for the glide ratio to be 13 to 1 or higher. A Baron with both props stopped and feathered is listed as 12 to 1 in the POH.

 

[brywd]

I tried stopping the prop during my phase one or test flight phase on my RV and the glide was dramatically better than with the prop windmilling even if pulled back. In a real life or death situation I'd certainly stop the prop. You will have to get down to near min. controllable a/s initially to get it to stop though and then trim for best glide.