I'm doing some more aviation math problems and am having a hard time finding information on the glide ratio for the Cessna 170B. I saw one reference on the 170 site to 7:1 but thought that it seemed kinda low compared to similar cessnas.

I've been creating some more lessons for my 7th grade students to apply the math they are learning. I might post them up for some insight on ways that I can improve what I'm developing.

Thanks.

Seems that's about right... (good reason for a Sportsman)

It says 7:1 in the book sportsman claims 13:1 with there stol kit, I have never actually checked but it is vastly better with the sportsman!
The biggest variable is the prop, the longer and finer pitch your prop is the lower the glide ratio.

River rat wrote:It says 7:1 in the book sportsman claims 13:1 with there stol kit, I have never actually checked but it is vastly better with the sportsman!
The biggest variable is the prop, the longer and finer pitch your prop is the lower the glide ratio.

I doubt that a Sportsman will increase glide ratio by that much. I have one on my 182 and like it but going from 7 to 13 is almost double.

Tim

qmdv wrote:

River rat wrote:It says 7:1 in the book sportsman claims 13:1 with there stol kit, I have never actually checked but it is vastly better with the sportsman!
The biggest variable is the prop, the longer and finer pitch your prop is the lower the glide ratio.

I doubt that a Sportsman will increase glide ratio by that much. I have one on my 182 and like it but going from 7 to 13 is almost double.

Tim

According to Sportsman web site it says " increase coficient of lift 37% " and from my own testing this seems about right. Much further when big fan stops turning .

The C170 POH does not have a max glide chart like in the c152,172,182 POH, correct? I've looked through one copy online but didn't see one.

Thanks

My glass back 182 is 8.2:1 with the prop at idle and the governor pulled all the way out. This has been measured more than a few times with the GPS unit.

I could imagine the 172 being pretty similar, and the fastback on the 170B even better, if that helps you any (probably not).

if it is for a math class estimate 7, 8 and 9 to one, then calculate the % difference and make a chart of how far it will go from any given height.

You'll have to take into account the weight as well. Lightly loaded, its glide ratio is substantially farther than loaded to gross weight.

Cary

Add bushwheels and some cow shit on the wings and the glide ratio becomes more brick like

Cary, you're usually spot on, but this time I have to respectfully disagree: You seem to have conflated Glide Ratio with Sink Rate--a common misperception.

Glide ratio of a given airplane configuration is substantially UNchanged with variations in gross weight. The best glide ratio [sometimes expressed as best Lift-to-drag ratio, or L/Dmax] is a function of the aerodynamics, not weight/wing loading. Sink rate will be less at a lower weight/wing loading, but the L/D doesn't change. For a given configuration, L/Dmax occurs at a specific angle of attack, virtually unchanged with wing loading.

This is the reason that many high performance sailplanes take on lots of water ballast for strong conditions: They really don't spend that much time climbing, and can cruise faster, with the same L/D, therefore covering more distance, and can penetrate through areas of sink with less net loss of altitude. [The sailplane guys that recently flew Reno to Casper in one hop had a pretty heavy wing loading, on top of >45:1 L/D, and they were running downwind, with wave]. The water ballast can be dropped should lift get weaker later in the day where better climb performance may be an advantage.

I believe there's a gliderport not that far from you, maybe you even know some of the soaring bums whom you could ask. Or worse yet, get hooked on another efficient way of spending money whilst having fun.

Thanks. cubscout