The International Cessna^® 170 Association

I would like to upgade my nose cowling to modernize my 170 a bit. does anybody know of a nice looking 172 nose cowling that would fit, and not be prone to cracking like the 54 nose cowlig from a b modle? Thanks

They all are prone to cracking.

The one that George hates, is a really good one! The one for belt driven vac pump. The install is here in the web sight somewhere and it gives the part Number's.

mit wrote:The one that George hates, is a really good one! The one for belt driven vac pump.

For the record Tim I don't like it either. In fact I don't particularly like the ''53 and later cowl. Give me a '52 and earlier version. No cracks and wear would be nice but do those things really go hand in hand with any Cessna cowl?

+1 for the '52 and earlier cowls.
And, as a bonus, you get really spiffy looking grills that go great with a skull cap spinner!

bagarre wrote:+1 for the '52 and earlier cowls.
And, as a bonus, you get really spiffy looking grills that go great with a skull cap spinner!

Don't forget the added weight/complexity of the interior air-box of the '52/earlier cowl, not to mention the expensive/undependable clamshell fasteners. I believe Cessna did the right thing in redesigning the cowling to a pressure-cooling system in '53, although it would have been nice if they'd made the nose-bowl more robust.

Of course for those who already have their airplanes, we're probably stuck with what we've got. If you're shopping for your 170.... then this is one of the choices you'll get to make.

I was thinking of a 59 172 cowling...

Just remember Kyle, the more "custom" things you do to your airplane now is just more work to put it back to stock when you decide you want to be "An originality nut for what ever reason". At your age it won't be for a while. This is something that comes later in life. But you've been warned

mit wrote:The one that George hates, is a really good one! The one for belt driven vac pump. The install is here in the web sight somewhere and it gives the part Number's.

I've been misunderstood on this matter.
It's not the nose bowl I dislike....it's the mechanical vacuum pump installation (which requires that 180/182/185 nosebowl ) that I dislike. The ugliness of that nose bowl is secondary, in my opinion.

In fact, ...it's ANY installation of a dry-mechanical vacuum pump I abhor in an airplane of this type. (Wet pumps are better...but only marginally so as regards reliability when compared to venturiis.) If the pump-fragility doesn't concern you, then perhaps you'll appreciate the fan-belt/pulley and the vibration it passes onto the engine nose-case that might interest you. And don't forget that the STC which supports that installation is obsolete as is the pump required for the installation. Almost NO ONE has parts for that pump and those that do don't want to work on it because that pump is a modification of the ones the typical repair-station is authorized to repair. There is no factory support for that pump or it's repair procedures. (Yeah...I want one of THOSE on my airplane!)

Why do I think a vacuum pump installation on a 170 is tragic? Well... primarily because this is not a hard-IFR airplane. It's a single-engined airplane which has little business launching into zero-zero IFR...which is when a pump is theoretically more desireable than a venturi. If one will restrict one's takeoffs into a more reasonable 500-1,000 foot ceiling.... then a venturi will have those gyro's already spun-up and operational before entering the clouds.... AND there is virtually NO possibility of that failure-prone pump giving up the ghost on you. IF you're flying..... you're vacuuming!

Next argument most commonly heard is ..."But what about ice?" .... which is a ridiculous concern in an airplane that is prohibited from flying in ice! Do NOT fly in icing conditions in this airplane regardless of what vacuum system you might have! Doh!

gahorn wrote:Next argument most commonly heard is ..."But what about ice?" .... which is a ridiculous concern in an airplane that is prohibited from flying in ice! Do NOT fly in icing conditions in this airplane regardless of what vacuum system you might have! Doh!

Agreed, but those who fly in cold climates should know that when the unexpected icing occurs, venturis will ice up before anything else, dropping the suction to about 1" very quickly. Venturis are much better than vacuum pumps for these airplanes, but for those who want a little extra protection, a standby vacuum system based on intake manifold suction solves two problems: it will replace the suction lost due to venturi icing (but only during a descent out of icing conditions -- http://www.thevacsource.com/), and it allows the gyros to be spun up prior to takeoff. That may have real value for some of us.

jrenwick wrote:[...Agreed, but those who fly in cold climates should know that when the unexpected icing occurs,....

That's why a secondary gyroscopic system utilizing an entirely different power source is required for IFR certification....(i.e., electric T&B/Coordinator)....to get back out of those clouds.

Realistically speaking.... if you didn't notice the ice forming on your windshield, struts, wings, pitot, etc etc.... then your venturiis (which are the least of your problems), which will still produce sufficient vacuum for quite some time especially on already-spooled gyros. I have to say again...worrying about iced venturiis is like worrying about dandruff. You'll see it far before it causes a real problem, and even then there's already a back-up plan in the T&B.

Challenge: Find an accident that was caused by continued flight into icing/IFR due to iced up venturiis.... And then compare that statistic to the ones caused by failed vacuum pumps ...in ANY kind of weather.
Hypothesis: Venturi failure due to icing has a ZERO record of accidents attributed to it. It's a figment.

gahorn wrote: I've been misunderstood on this matter.
It's not the nose bowl I dislike....it's the mechanical vacuum pump installation (which requires that 180/182/185 nosebowl ) that I dislike. The ugliness of that nose bowl is secondary, in my opinion.

In fact, ...it's ANY installation of a dry-mechanical vacuum pump I abhor in an airplane of this type. (Wet pumps are better...but only marginally so as regards reliability when compared to venturiis.) If the pump-fragility doesn't concern you, then perhaps you'll appreciate the fan-belt/pulley and the vibration it passes onto the engine nose-case that might interest you. And don't forget that the STC which supports that installation is obsolete as is the pump required for the installation. Almost NO ONE has parts for that pump and those that do don't want to work on it because that pump is a modification of the ones the typical repair-station is authorized to repair. There is no factory support for that pump or it's repair procedures. (Yeah...I want one of THOSE on my airplane!)

Regarding the asthetics, please allow me to respectfully disagree. The attached picture is one of my favorite beauty shots of my bird, which all can plainly see has the aforementioned belt-driven pump and early 172 nose bowl. There's at least one other flying the same setup here in Ohio but I never seem to have a camera handy when I see him at the occasional fly-in. His plane looks even better combined with the clean lines of his Bartone exhaust.

Would I go to the trouble of seeking out the parts required to do this STC all over again? No, not likely as I would agree a venturi would do all I need it to do. Thankfully my pump (installed in the 1970's) hasn't needed any service in my brief ownership experience. We installed a new belt at the last annual, which runs slightly loose. As for additional load or vibration at the crank, of course I have no comparative data, but I doubt it's much. Likely no more than any belt-driven accessory on any other aircraft. Compared to the forces imparted by a propeller (when's the last time yours was balanced?), it's likely nil.

My 2-cents

N5417B

When I purchased my plane 28 years ago, it had a 1959 Cessna 172 nose bowl. It worked great, never cracked, but I sure got the ribbings from the Texas guys at the local fly-in's. When I refurbished my plane +/- 6 years ago, I removed the "59 nose bowl and installed a NOS "55 unit Sold the "59 nose bowl to Paul Wood in Texas. Look him up in the Directory and give him a call or email him....he may still have it.

Bruce Fenstermacher wrote:Just remember Kyle, the more "custom" things you do to your airplane now is just more work to put it back to stock when you decide you want to be "An originality nut for what ever reason". At your age it won't be for a while. This is something that comes later in life. But you've been warned

if I did that, I would have to tak off everything I just did!

As a matter of curiousity, on an aircaft using engine intake manifold pressure as an emergency vacuum source,what seems to be the critical altitude at which one can reduce the throttle setting to acquire the necessary differential vacuum to operate the vacuum gyros and still maintain altitude?