What is the seaplane lip?

bagarre · Post by **bagarre** » Wed Sep 05, 2012 1:14 am

I've been going thru the TCDS for other things and noticed the wording about the 'seaplane lip'.
It would appear that the little lip itself IS the seaplane lip.

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

This appears to be the older 170 and 170A cowling.

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

The way that is worded, the 3/4"-45Â° lip on bottom cowl IS the seaplane lip. Which means you don't need a lip at all down there unless you are a sea plane or running a Koppers or Beech propeller as those call out the lip directly

...item 108 with seaplane lip

Wed Sep 05, 2012 12:32 pm

Huh. Good catch David.

Drawing 0552000 is for serial numbers 18003 to 19200 (48 and 48 model year) and it has the 3" lip part number 0552000-41 and. Drawing 0552001 is for serial numbers 19201 and on (50 and on) which includes the 3/4" lip part number 0552001-41 according to the A model IPC. The B model IPC has drawing 0552001 and it has the same 3/4" lip part number 0552001-41.

In the A model and the B model IPC, the Kit, Floatplane Fitting Installation, Cessna dwg 0541125, list the lip as part number 0552001-60. So we presume it is not the same as the 3/4" lip from the standard cowl 19201 and on. Also though in no way official, the IPC drawing of the B model cowl on the seaplane looks like it has a larger lip.

According the the TCDS for both the A and B for seaplanes (the 48 is not approved by the TCDS for floats) there is no requirement for a special lip in the required equipment area.

Since the 48 is not approved for seaplane operations this leaves only a 49 A model that might have the larger 3" lip and perhaps that is why the note is on item 108. Doesn't explain why it is not listed in the required equipment list. Being the TCDS is at revision 54 would indicate there have been other mistakes as well.

Conventional wisdom is that a seaplane lip is bigger than standard. Why? Because presumably the larger lip would cause more vacuum in the cowl sucking more cooling air through the cowl. Or just perhaps, since most 170s have a smaller lip, that when a early larger lip cowl appeared it what just thought to be the mysterious seaplane lip and that fit the aerodynamic reasoning previously mentioned.

I don't know. Does a seaplane even run hotter that a land plane? Maybe Cessna wanted the seaplane to run hotter because it was going to be operating in the cooler environment of water.

Maybe the smaller 3/4" lip actually runs cooler than the larger 3" lip. I know of two 49 A models that should have the larger lip but one has the 3/4" and the other something less the 3" but more that 3/4" and they both run cool and it's not been exclaimed why. Of course this doesn't explain why most 50 and 51 A models with the smaller lip but otherwise the same internal pressure cowl run the same temperature range as the later B model pressure cowl. So many questions and never a 1950s area Cessna engineer when you need one.

So what is a seaplane lip? Though it goes against conventional wisdom, it appears to be the standard 3/4" lip found on every 170 serial 19201 and on.

That's good news for most of you as it would seem you can know all boost your running a seaplane lip.

Know I wonder just what that lip, part number 0552001-60 listed with the seaplane kit really is?

jrenwick · Post by **jrenwick** » Wed Sep 05, 2012 4:22 pm

I would think this is probably an error in the TCDS. Seaplanes need more cooling than landplanes because they have a lot more drag. They cruise slower, and at a higher fuel burn rate, so they're going to run hotter unless they get more cooling air. The bigger lip should have that effect.

Makes sense to me, anyway. I hope I'm right.

Post by **GAHorn** » Wed Sep 05, 2012 6:10 pm

The TCDS has indeed incurred many errors over the years. (Rev 54 was instigated by a letter I personally wrote FAA_OKC to correct the wrongful information regarding flaps settings on early B-models. There are additional errors which have been noticed since.)

In common parlance, I believe the early 3" lip has become anecotally known as the "seaplane lip".

bigrenna · Post by **bigrenna** » Wed Sep 05, 2012 9:55 pm

delete

Wed Sep 05, 2012 10:03 pm

So Greg what is the part number of your lip? And how do you know your cowl wasn't swapped at some point with a 48 or 49?

ghostflyer · Post by **ghostflyer** » Wed Sep 05, 2012 11:13 pm

Bruce, The points that you have raised are very good as when I did the conversion on my aircraft [180 hp] the lower cowl had to be modified. But due to many patches over the years from previous owners and a 4 in lip , I went to the type certificate for information and was totally confused. I now run with a 1 in lip slanted at 45 degrees . I had it at 90 degrees to the airflow and it caused too much turbulance ,but still cooled the aircraft engine to norminal figures. However the noise was a roar . So the 45 degrees was tried and was successful . the gap between the lower cowl and fire wall is only 3 ins. The original hole was massive ,I cant remember the size but about 9 ins . PS. Have you seen the You Tube clip with the 170 flying [ in South America]with the Coralla engine fited and flying WITHOUT cowls. Thats cooling for you.

hilltop170 · Post by **hilltop170** » Thu Sep 06, 2012 10:11 am

Here you go;

http://www.youtube.com/watch?v=9UYWMM4ggcw

http://www.youtube.com/watch?v=nsPRRO6aM8o

It will mean more if you know Spanish. The Corolla engine makes the 170 sound like an ultralight with a 2-stroke engine and has a centrifugal clutch so the prop freewheels with the engine not running.

marathonrunner · Post by **marathonrunner** » Thu Sep 06, 2012 10:23 am

The lip does come with the seaplane kit. I installed it on mine when I installed the kit

Post by **Bruce Fenstermacher** » Thu Sep 06, 2012 1:12 pm

So Joel to clarify since you might be one of the few who have done this.

You bought the kit AK70B53-3 which includes the seaplane lip 0552011-60. And what size and angle is this lip. 3" and 40Â° like the 48 and 49 lip? 3" and 45Â° which would be a deeper lip set at the later angle? Or is it something else?

Harold Holiman · Post by **Harold Holiman** » Thu Sep 06, 2012 3:19 pm

My 1949 170A had the small 3/4" lip.

marathonrunner · Post by **marathonrunner** » Fri Sep 07, 2012 1:42 am

Bruce

When I installed my float kit I borrowed an existing one a friend had bought used and had not been opened. We opened it and I duplicated on paper all the parts and labeled them with part number and thickness and type of material. I have sent those around to several other persons who wanted to install float kits. Currently they are with a member in Massachusetts. I am not in the states at this time so am unable to access all the information. The lip was a flat piece on I believe 3" aluminum that was riveted to the existing lip on the cowling. Sorry I will email him and try to get more information on that particular part.

DaveF · Post by **DaveF** » Mon Jan 27, 2014 4:58 pm

Does anyone have information on the lip? Part number, size, material, drawing, etc.?

Edit: My question is really directed to Joel -- did you locate the documentation you referred to above?

N8293A · Post by **N8293A** » Mon Jan 27, 2014 6:45 pm

Is it possible the larger seaplane lip is intended to keep water spray from getting to the firewall? The larger lip would do a nice job of directing any spray down and away from the cowling exit, and maybe keep some spray off the belly of the aircraft.

blueldr · Post by **blueldr** » Mon Jan 27, 2014 7:02 pm

It's used to add drag to keep from exceeding the red line on float planes.

The International Cessna 170 Association