Lower Cowl Lip size

[Bruce Fenstermacher]

Paying much closer attention to 7A's gauges now that I'm going to be an owner I noticed that it was running pretty cold. 140 degrees with ambient temperatures in the 60s. Assuming the 40 year old gauge to be bad we simply replaced it with new.

Well guess what. The new gauge shows oil temps running about 140 and less in ambient temperature of about 50 degrees. Of course we didn't check the new gauge before we put it in which was stupid, so we are assuming it is good. That lead me to look closer at the lower cowl lip and compare it to the one on my old airplane.

This 7A has a cowl with a lip that is twice the size of my old plane both having the same cowl design of the '52 and prior variation. Of course I question most stuff on my old plane and so am not sure it represents a standard lip.

So what is a standard lip? My old plane cowl lip is about 3/4" my new plane has one about 1-1/2".

Of course a picture or two would be worth a thousand words but I didn't think to take any.

[n3833v]

Bruce,
Mine is about 1-1/2. I just know I have to keep cleaning the bugs off it. My temp runs about 180 t0 200 in this weather without any plug.

[3958v]

Bruce I too have the larger lip and I have low oil temps in this weather too. Temps are about what you are reporting. I guess the good side is that I never have high temps like some even when the outside temps go above 100 deg F. I sure wish Cessna would decide to manufacture the inlet baffles again. I keep hoping to find a pair on E-bay but so far no luck. Bill K

[jlwild]

Bruce,

The cowl lip on my '55 170B extends about 3/4 " below the lower cheek cowl edge. I am currently in New Haven, CT with grandchildren; so, not able to take picture. Also, if I remember correctly, Cleo Bickford told me there are two cowl lips for the C-170. The narrow 3/4" like I have and a wider one made for float plane C-170's. Perhaps the 1 1/2" lip is the float plane setup?

[SteveF]

Bruce,

I have an early 170B serial # 20505 and it has the 3/4 inch lip. It also has cool oil temps even in summer. I have the Cessna winterization plate to put over the oil cooling inlet and it says on the front remove above 60 degrees Fahrenheit. If it is ok to 60 instead of 40 or so I think this thing must run colder than you might expect. I don't think the lip size makes much difference on the oil temp. I also have an O-300-B with the Association STC.

SteveF

[Bruce Fenstermacher]

I didn't directly ask but the purpose for my post was to determine what a standard lip is and what a seaplane lip is and have it documented here. So far it looks like 3/4" is standard and 1-1/2" would be the seaplane lip at least on B models.

Both John and Bill have '48 170s and wondering if it is just a coincidence they both have the larger lip or maybe Cessna started with the large lip then reduced it later creating the smaller standard and larger seaplane lip. Anyone with a '48 know any different?

Steve the larger lip, I would think, would create a lower low pressure area under the cowl sucking more air through the cowl for cooling. It would also mean more drag which is why Cessna would have wanted to reduce it or have it as small as possible.

[Ray Davidowski]

Both John and Bill have '48 170s and wondering if it is just a coincidence they both have the larger lip or maybe Cessna started with the large lip then reduced it later creating the smaller standard and larger seaplane lip. Anyone with a '48 know any different?

The majority of '48s I've seen pics of (and even a number of As, perhaps earlier serial #s?) have the large lip.

Just checked the illustrated parts catalogs, and p/n 0552000-41 was the standard lip on '48s and As to sn19200. From then on 0552001-41 was standard on As and Bs (and is depicted smaller).

I only see mention of floatplane equipment in the A catalog, and that lip is 0552001-60. Go figure?

[Bruce Fenstermacher]

Thanks Ray. Your fitting right in looking at the IPC. Gee why didn't I think of that.

[DWood]

Bruce:
The 48 used the larger lip along with the A (per the part number 0552000-41. I have been looking for a larger lip for my 48 project and recently bought a smaller lip that I will use unless I can find the larger one. I have heard that the 48 used the larger lip for cooling purposes. The sea plane lip that is offered for the B model is flat aluminum riveted onto the existing lip per my conversation with Wipaire.
Let me know if you want to trade for the shorter one.
Dan

[Harold Holiman]

My former 1949, N9027A, had the 3/4 inch lip. More of the other 170A's I remember had the larger lip rather than the smaller lip.

Harold

[Bruce Fenstermacher]

Dan thanks. This is all very interesting. A detail I hadn't noticed before in my studies of all things 170.

If I was interested in the shorter lip, Dan I doubt you would be interested in the larger one I have. From memory of looking at mine the other day I'm wondering if this part wouldn't be easy to make.

[DWood]

Bruce;
I had looked into making one, but it doesn't look very easy. If anyone has ideas on how to do it, please let me know.
Thx,
Dan

[doug8082a]

Didn't the change in the size of the lip coincide with the increase in the size of the lower cowl opening? I don't have an "A" IPC to refer to, but I know the '48 had a smaller (different?) lower cowl opening and the larger lip and I thought that carried on to the "A", but I don't know when things changed.

[n2582d]

The majority of '48s I've seen pics of (and even a number of As, perhaps earlier serial #s?) have the large lip.

Just checked the illustrated parts catalogs, and p/n 0552000-41 was the standard lip on '48s and As to sn19200. From then on 0552001-41 was standard on As and Bs (and is depicted smaller).

I only see mention of floatplane equipment in the A catalog, and that lip is 0552001-60. Go figure?

I'm trying to make sense of the TCDS regarding which is a seaplane lip. Here's what the TCDS says under "Specifications Pertinent to All Models":

107. Engine cowl per Cessna dwg. 0552000
Includes 3"-40° lip on bottom cowl

108. Engine cowl per Cessna dwg. 0552001 or 0552002
Includes 3/4"-45° lip on bottom cowl
required for seaplane

I would think that item 107 with the 3" - 40 degree lip would be the seaplane lip yet it is the smaller 3/4" item 108 that is "required for seaplane". Here's my hypothesis: Comparing Cessna dwg. numbers to part numbers item 107 (dwg. 055200 / p/n 055200-41) is for straight 170's and A models through s/n 19200. The 3/4"-45 degree lip of item # 108 is the standard lip on planes after s/n 19200; this has nothing to do with the seaplane version. (Compare Cessna dwg. # 052001 and p/n 0552001-41). Item 108's reference to the 3/4" - 45 degree lip being "required for seaplane" is not saying that the 3/4" lip is the seaplane lip but that it is necessary for the seaplane lip, p/n 0552001-60, to screw onto.

Trivia question: The TCDS lists required equipment for the 170; such things as propeller, wheels, tires, tailwheel assy. It does not list the cowling as a piece of required equipment. Could one legally fly without the cowling on? The TCDS gives one the impression that it is optional equipment like the oil dilution system.

I'm trying to figure all this out because I recently acquired an Koppers Aeromatic F200-H propeller which requires the seaplane lip.

[Robert Eilers]

I purchased my 170B from an individual living in Phoenix. He had tried a number of things to assist in reducing oil temps during the Arizona summer temps - including a sea plane lip. He had manufacturued at 2 & 1/2" lip, drilled holes along the original lip and installed the so-called sea plane lip with small bolts and nuts. H explained the extended lip did little to improve the oil temp. He had the most success with widening the Oil tank intake port in the front of the nose cowl. I still have to wider opening and during the winter need to reduce it to maintain reasoanble oil temps up here in Northern Ca.