'57 Hawk - IFR or not?

'57 Hawk - IFR or not?

I have a 1957 172 (with venturis, of course). My flight instructor is telling me that it cannot legally be flown IFR. Does anyone know if this is true and if so is there anything that can be done to make it legal, perhaps an electric vacuum system? A standard vacuum system is out of the question as the engine will not support the pump.

Steven Washer
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Re: '57 Hawk - IFR or not?

Hi Steven;

As far as I know, there is a minimum equiment list for IFR flight, and as long as your airplane systems can support this equipment, you can fly it IFR.  Basically, the only two required instruments that run off of the vacuum system are the Attitude Indicator and the Directional Gyro.  There are electric AI and DG instruments that could be installed in your airplane.

The only downside to this is in a partial panel situation after losing your electrical system.  The Turn Coordinator is sort of a backup for the two vacuum instruments in that it indirectly indicates bank attitude and can be used (along with the compass) for timed turns to headings.  In this scenario you will lose all indications of bank on your instrument panel (except for your compass).

There is probably a placard in your C-172 indicating it is not certified for IFR flight because it was not equipped for it when Cessna delivered it from the factory.  However, FAR 91.205 Subpart C--Equipment, Instrument, and Certificate Requirements lists all the required equipment for IFR operations.  It makes no mention of a vacuum system, but does require an electrical system and the instruments, gauges, lighting, communications, and navigation equipment necessary for IFR flight.  Therefore, I would think that you could equip your airplane for IFR flight if you installed all the required equipment.

I hope this information is helpful.

Jon

Jonathon Plaxton
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Re: '57 Hawk - IFR or not?

I'm just a VFR pilot, not expert at anything IFR, but I also own a '57 C172 and have looked into this question on and off over the years. I totally agree with what Jonathan said. Furthermore, I believe if you look carefully into the FARs you'll be surprised at how little extra equipment you actually need to legally fly IFR compared to what most vfr planes already have. Most IFR planes carry significantly more equipment. The reason for this is redundancy, safety, and is probably well justified. At any rate, even with minimal IFR equipment you can certainly fly IFR in marginal or good weather to stay current and with a willing instructor to save rental fees and get your ticket. This is an opinion.

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Re: '57 Hawk - IFR or not?

i have a 56 skyhawk with the venturis. i had them removed after i had issues with attitude not spooling up in the bank etc. I had a dg and a attitude indicator installed electric. they are stc / pma approved. in addition i installed a new alternator to carry the new loads. according to the avionics mechanic who installed the devices and after reviewing the regs it does meet min ifr, although personally i would not do HEAVY ifr as if the alternator failed you would be on battery alone. another option i suppose would be to install the attitude indicators with battery back up installed. - hope this helps..

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Re: '57 Hawk - IFR or not?

Of course you can fly IFR if your gyroscopic instruments work well and you are otherwise equipped in accordance with FAR 91.205.  I have been current as a CFII and A&P for 25 years and I would take the reliability of venturis over a vacuum pump any day.  The big caution is to stay way away from icing conditions. --notice that a heated pitot tube is not required either because uncle sam has given us the lattitude to use common sense about this.
  The Type Certificate Data Sheet for the basic 172 has no limitations regarding IFR flight and its limitations placard (you should have one displayed) does not mention the familiar words that one reader alluded to regarding approved operations.  It does not show up until the 1971 model and it says: "Known icing conditions to be avoided. This airplane is certified for the following
flight operations as of date of original airworthiness certificate:
(DAY NIGHT VFR IFR)" (as applicable)".
Now, if your vacuum (venturi)powered gyros do not work well in flight, that's a different story.
--DRB

Dean Brock
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Re: '57 Hawk - IFR or not?

A few years ago I had a 1959 172 with Venturi's and I was visiting a airport and saw a early 172 wih no venturi's so I checked it out.  It had a mod that had a pulley mounted behind the prop and a belt going to a vacuum pump mounted in the right airscoop, it had to be an STC item.  There is a company who has a STC on a alternate (emergency vacuum) system that takes suction off the intake manafold to run your vacuum instruments when your other suction systems die.  Venturi's are at least reliable until they get iced up. I've alway wondered if you mount them so they were right behind the exhaust pipes the heat could keep icing from ever forming.

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Re: '57 Hawk - IFR or not?

I had a customer with the exact same problem and model plane. he bought the plane as a student pilot and wanted to get all his ratings thru CFII.
we install avionics and made this approved for IFR. I am not sure the exact FAR but it states that the attitude indicator must be spooled up and operating correctly before takeoff! not in these exact words you would have to look it up. the problem with the venturies is you must be moving to get the required vacuum. by installing an electric attitude indicator you will solve this problem. they are expensive so we installed a switch to use the electric indicator only when needed for IFR or as desired. a heated Pitot tube is required any time in visual moisture (clouds,fog,rain etc.) this doesnt mean icing!!! if you get into icing the plane is not certified for known icing so you would have to get out of the ice. most people would do that anyhow with a 172. my student now has his 172 on a 135 certificate for scenic flights and lives in alaska currently. he had about 400 hours of actuall with this plane.  so your limiting factor is a artificial horizon and a heated pitot tube if you want to ever practice actual or takeoff in fog.  hope this helps

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Re: '57 Hawk - IFR or not?

I'm a&p IA and I agree with the other A&P as I am also a 8353 hour ATP and you are not required to have a heated pitot to fly in visible moisture.   It makes sense but it is not a requirement.

Visible moisture and 10 degrees celcius is considered by most to be known icing conditions.  That is only 50 deg F.

So if you knowingly take the aircraft into  visible moisture at 10 and below it is a bad thing.

I fly my 56 C-172 regularly in visible mosture going back and forth to work to allow me to climb above the MVA min vectoring alt direct between my corporate job and my home to not have to worry about the scud

I have two venturi systems with one vaccum dg and two vacuum horizons and a Garmin 296 for reference only

So with the venturis which I would take any day over dry air pumps and even a wet pump which I would like to have I simply can't take off with so little vis that I would not be spooled up before the clouds.

Putting the venturis behind the exhaust is a novel idea.

As an emergency using the manifold intake vacuum is good but you wouldn't want to use it all the time because even though it is vacuum and nothing from the engine is being brought into your instruments I watched a 172 configured this way eat amny instruments after it was installed. Probably because f the beat of the drum of the valves opening and closing even though it was a O-300.

Beside what if the engine quits then you got nothing.  Oh yeah that's the same for a wet pump and a dry pump.

I also have a digital KR87 ADF and a Narco late model digital ILS receiver with GS

I don't have a DME other than the 296 so if I did a non precision I would have to be at an altitude that would have me be in radar environment at the FAF (you have to be at or above the alt on the chart as long as the controller knows what you are doing ahead of time for other aircraft) and have the controller call the fix before descending to MDA  Not very good so I am loking to put in a DME receiver

I also installed an alt static port

I have the regualr pitot and cessna furnished the aircraft with an OAT probe in a vent that must be open to sense the OAT

I think the Garmin 430 and 530 Garmin would be nice but compared to antiquated airline simple dme dme fms they suck

I do keep my approach speed up for venturi but I have never ever seen a problem in turns or any attitude with the venturis and vaccum horizons either of them

This also goes for my Navion with venturi vacuum

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Re: '57 Hawk - IFR or not?

MY two venturi vaccum systems are completely seperate and redundant to each other

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