Checking Knowledge

[170C]

I,like most of you, have both editions of the Cessna 170 books, have flown a number of 170's, have looked at hundreds of 170's and I have listened to facts and figures from numerous sources. I had someone (gently) challenge my knowledge recently and not wanting to make a big deal of it I simply didn't argue the point because I might have been wrong I have long been under the impression that the Cessna 170A did not have any wing dihedral. The B model was the first one with wing dihedral. Additionally, as we all know, visibility in all 170's (and early 172's; 180's) is superior to later model Cessna aircraft. The glare shield tapers from its start all the way to the forward end of the engine cowling. This same individual maintains the A model cowling tapers more so than later B models do. Who is correct?

[bagarre]

To the best of my knowledge...

The A models had no dihedral.
The B models were given dihedral as well as 3 degrees of washout.

No idea if the A had better viz but how would that explain the 52 B model that retained the A cowl and panel?

[hilltop170]

Wingnut would know much better than me but what I understand is the top of the A Model wing is flat from tip to tip. Any effective dihedral would come from the bottom of the wing tapering from full thickness at the strut and thinning toward the tips. Not much to speak of and definitely more unstable in roll than the B Model.

[Ryan Smith]

I,like most of you, have both editions of the Cessna 170 books, have flown a number of 170's, have looked at hundreds of 170's and I have listened to facts and figures from numerous sources. I had someone (gently) challenge my knowledge recently and not wanting to make a big deal of it I simply didn't argue the point because I might have been wrong I have long been under the impression that the Cessna 170A did not have any wing dihedral. The B model was the first one with wing dihedral. Additionally, as we all know, visibility in all 170's (and early 172's; 180's) is superior to later model Cessna aircraft. The glare shield tapers from its start all the way to the forward end of the engine cowling. This same individual maintains the A model cowling tapers more so than later B models do. Who is correct?

Given that I've seen an airbox nosebowl on a pressure cowling, would have to disagree with the cowling taper. There appears to be some difference in these two cowlings dimensionally in the front if one pays attention to the XP Mods IO-360 install thread on here.

If your friend said that the 170 cowlings taper more than later model 172 cowlings, I would be in agreement as the Lycomings fit in the later model 172s without bumps on the cowling.

[Ryan Smith]

Unless you're talking about vertical taper from the side profile, in which case, I think the pressure cowling has a slight crown that the airbox cowling does not. The difference there is negligible at best from what I can see.

[Bruce Fenstermacher]

As stated. It is commonly said that the A has no dihedral though as Richard points out it may have some given the wing taper.

I don't recall off the top of my head if the thrust line changed with the B model. The engine mount is a different part number 0551000 verses 0551000-50 but that does not mean they are different. At least in the angle and position they hold the engine. The reason I bring this up is one could measure from the top of the crank flange to the top of the front cowl lip on a A and B and see what the difference is. If any that would indicate which had a steeper slope. I think their the same personally.

[48RagwingPilot]

FWIW, my '48 170 has dihedral but not a tapered wing. Visibility over the cowl is outstanding.

[jrenwick]

The later B models have "lady legs," which raise the nose of the airplane a little bit as compared to the A-model gear legs, don't they? That would change the angle of the top of the cowling, and would produce the illusion that it tapered less.

[Bruce Fenstermacher]

John I never thought the lady legs where longer, they could be. Of course they are stiffer and usually have a different stance on the ground. I thought we were talking about the actual angle from the windshield to the front of the cowl and the view from the pilots seat over it. I don't think there is a significant difference in this angle from the early cowl to late version.

[jrenwick]

Bruce, I know the actual shape of the cowling is the same; that's why I called it an illusion. I'm not positive the lady legs raise the nose at all, but it seems like they would, at least from the increased stiffness and inward vs. outward bend. 180 gear legs and 8.00 tires have even more of an effect, if those have been installed. From the pilot's perspective, the top of the cowling would slope downward less than with a stock A-model.

[170C]

The slope/taper, if that is the proper term, that I referred to would be, as Bruce stated, from the windshield to the nose of the cowling without regard to what gear legs were on the aircraft. It may be an illusion, but it appears to me that the taper begins at the glare shield and continues all the way to the nose of the cowling. The person who felt the A model had wing dihedral and more cowling slant/taper is a long time A&P, but I "think" he may have just had the illusion of both items.

[GAHorn]

Cessna 170
Dihederal …………………………………………………………..0 degrees
Fabric wings have no built in twist.
Angle of incidence for the stabilizer . . . . . . . . . . . . . . . . . . . . . . . . –4 degrees
Length of struts – front . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.47 inches
Length of struts – rear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106.58 inches
See Note 1.

Cessna 170A
Dihederal …………………………………………………………. 0 degrees
Angle of incidence – root . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+1 1/2 degrees
Angle of incidence – tip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+ 1/2 degree
Twist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 degree
Angle of incidence – stabilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .–4 degrees

Cessna 170B
Dihederal ………………………………………………………… .+ 3 degrees
Angle of incidence – root . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . +1 1/2 degrees
Angle of incidence – tip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 1 1/2degrees
Twist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . 3 degrees
Angle of incidence – stabilizer . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . – 2 deg. 48 min.