Certify a straight tail 172 for IFR?

German guy

German guy

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Oliver
My wife and I are just about to buy a 1957 straight tail 172 (venturi vacuum). We would also like to use it for (light) IFR. I am aware of the advantages / disadvantages of a venturi driven vacuum system and also read quite a bit about this topic in the Cessna 170 forum, were a number of pilots had their 170s IFR certified.

This is what 91.205(d) requires for IFR flight:

(d) Instrument flight rules. For IFR flight, the following instruments and equipment are required:

(1) Instruments and equipment specified in paragraph (b) of this section, and, for night flight, instruments and equipment specified in paragraph (c) of this section.
(2) Two-way radio communication and navigation equipment suitable for the route to be flown.
(3) Gyroscopic rate-of-turn indicator [...]
(4) Slip-skid indicator.
(5) Sensitive altimeter adjustable for barometric pressure.
(6) A clock displaying hours, minutes, and seconds with a sweep-second pointer or digital presentation.
(7) Generator or alternator of adequate capacity.
(8) Gyroscopic pitch and bank indicator (artificial horizon).
(9) Gyroscopic direction indicator (directional gyro or equivalent).

The airplane we are interested in has all of this, assuming a successful pitot / static check.
The only thing which is missing is the 'navigation equipment suitable for the route to be flown.' We are planning to install a Garmin GNS 650, so that this requirement would also be met.

My question is whether I have overlooked something and if somebody else has also gone through the process of having his (straight tail) 172 certified? I believe that all 172s are certifiable, but don't know how to check on this - can I look this somewhere up?
 
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German guy said:
My wife and I are just about to buy a 1957 straight tail 172 (venturi vacuum). We would also like to use it for (light) IFR. I am aware of the advantages / disadvantages of a venturi driven vacuum system and also read quite a bit about this topic in the Cessna 170 forum, were a number of pilots had their 170s IFR certified.

This is what 91.205(d) requires for IFR flight:

(d) Instrument flight rules. For IFR flight, the following instruments and equipment are required:

(1) Instruments and equipment specified in paragraph (b) of this section, and, for night flight, instruments and equipment specified in paragraph (c) of this section.
(2) Two-way radio communication and navigation equipment suitable for the route to be flown.
(3) Gyroscopic rate-of-turn indicator [...]
(4) Slip-skid indicator.
(5) Sensitive altimeter adjustable for barometric pressure.
(6) A clock displaying hours, minutes, and seconds with a sweep-second pointer or digital presentation.
(7) Generator or alternator of adequate capacity.
(8) Gyroscopic pitch and bank indicator (artificial horizon).
(9) Gyroscopic direction indicator (directional gyro or equivalent).

The airplane we are interested in has all of this, assuming a successful pitot / static check.
The only thing which is missing is the 'navigation equipment suitable for the route to be flown.' We are planning to install a Garmin GNS 650, so that this requirement would also be met.

My question is whether I have overlooked something and if somebody else has also gone through the process of having his (straight tail) 172 certified? I believe that all 172s are certifiable, but don't know how to check on this - can I look this somewhere up?
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There is no required IFR special inspection other than the ones you have listed. It is the pilots responsibility to insure those requirements have been met. Transponder check, and altimeter checks, and the, equipment required to do the approach.
 
Hello Tom,

Thank you very much for your quick response.

Tom-D said:
There is no required IFR special inspection other than the ones you have listed. It is the pilots responsibility to insure those requirements have been met. Transponder check, and altimeter checks, and the, equipment required to do the approach.
Click to expand...

I am relieved to hear that. I thought that it is more difficult, because I heard that (for example) Diamond DA-20s cannot be legally operated IFR, even though many of them have all the required equipment!? :dunno:

Oliver
 
German guy said:
Hello Tom,

Thank you very much for your quick response.



I am relieved to hear that. I thought that it is more difficult, because I heard that (for example) Diamond DA-20s cannot be legally operated IFR, even though many of them have all the required equipment!? :dunno:

Oliver
Click to expand...

Diamonds can't be certified ,because they are composite,and have no metal embedded in the skin.
 
If you're going to dump the money into a GTN 650 I don't see why you wouldn't spend some money on coming up with a better attitude source than a venturi.

I've flown a few 172s of that vintage with a venturi for the gyros and quite frankly I wouldn't fly any of them in IFR unless it were a very thin layer with bases at least 1000 AGL.
 
Or just go with all electric gyros. You lose redundancy but with a 496 or something similar you have one hell of a back-up system.

I sold my 57 c172 exactly because of the venturi and no STC to install a pump. Had I owned a handheld GPS at the time and understood the capabilities of it, I would've never sold it.

I'd've made it all electric and kept it as a back-up to my 182.
 
The 0-300-A found in the 170 and early 172 can have the 0-300-D starter drive installed and run a vac pump. but that will not drive the early MA1 gyros, so you upgrade to the new style gyros. can you say $$$$$ :)
 
timwinters said:
Or just go with all electric gyros. You lose redundancy but with a 496 or something similar you have one hell of a back-up system.

I sold my 57 c172 exactly because of the venturi and no STC to install a pump. Had I owned a handheld GPS at the time and understood the capabilities of it, I would've never sold it.

I'd've made it all electric and kept it as a back-up to my 182.
Click to expand...

If it were me I'd go electric DG and attitude and leave the Venturi attitude.
 
By my understanding the only real disadvantage of the venturi systems is that the gyros only begin to spool up, once the aircraft takes off. In low IFR conditions, the aircraft might therefore enter IMC, before the gyros have reached full rpm and became sufficiently stable. Icing conditions might also freeze them up.

On the other hand, their simplicity makes them pretty bulletproof what is, from what I heard, not necessarily the case with vacuum pumps.

We are planning to use the the aircraft only in very light IMC, like to climb / descend through a ceiling at at least 1,000 ft.

I like the idea with an electric DG.
 
"Light" IFR - is that where you only sorta can't see as opposed to can't see at all?

And just to be clear, it isn't that DA-20s don't have metal, it's that they don't have lightning protection...which is metal. But if they had metal without it being sufficient for lightning protection, they still couldn't be certified. Good AvWeb link on it: http://www.avweb.com/news/reviews/182565-1.html
 
When I bought my 170 it had the original C-145 (predicessor of the O-300) with an STC'd vacuum pump that was driven by a V-belt from a pulley just behind the propellor much the same as the belt driven alternator on Lycoming engines. I don't recall the name or number of the STC but assume it's still available? It required changing the nosebowl to a later model 172 with bigger openings for cooling air since the vacuum pump was mounted up in front of the cylinders on the starboard side. FWIW I don't think I'd fly serious IFR without an engine driven vacuum pump.
 
peerlesscowboy said:
When I bought my 170 it had the original C-145 (predicessor of the O-300) with an STC'd vacuum pump that was driven by a V-belt from a pulley just behind the propellor much the same as the belt driven alternator on Lycoming engines. I don't recall the name or number of the STC but assume it's still available? It required changing the nosebowl to a later model 172 with bigger openings for cooling air since the vacuum pump was mounted up in front of the cylinders on the starboard side. FWIW I don't think I'd fly serious IFR without an engine driven vacuum pump.
Click to expand...

I could find no supported STC when I was considering converting mine (about 12 years ago). I found an old STC but it was no longer supported. I was under the auspices of the LR FSDO at the time and they weren't keen on doing a field approval based on that old STC.

If there was a valid one out there, I sure didn't find it.
 
timwinters said:
I could find no supported STC when I was considering converting mine (about 12 years ago). I found an old STC but it was no longer supported. I was under the auspices of the LR FSDO at the time and they weren't keen on doing a field approval based on that old STC.

If there was a valid one out there, I sure didn't find it.
Click to expand...

You should have used the STC you found, the A&P-IA can return the Aircraft to service by signing the 337 and sending it to OKC not the FSDO.
The FSDO can not tell you that you can't use a STC. Speciality one in public domain.
 
Tom-D said:
You should have used the STC you found, the A&P-IA can return the Aircraft to service by signing the 337 and sending it to OKC not the FSDO.
The FSDO can not tell you that you can't use a STC. Speciality one in public domain.
Click to expand...

How do you buy an STC that is no longer available, especially if it includes parts (i.e. mounting brackets, etc.)? How does one determine if it's in the public domain?

Serious questions...not being combative...won't help me now but it might help the OP.

It's been a long time and my memory is fuzzy but I recall it being a no-go at the time.

And, to clarify, we went to the FSDO asking about a field approval, not an STC approval.
 
timwinters said:
[...] Serious questions...not being combative...won't help me now but it might help the OP. [...]
Click to expand...

:yes:

Even without the the specifics of a venturi system, I believe this topic to also be of interest for other pilots.

I just spoke with the seller, the earliest pick-up date I could make was too late for him and he doesn't want to wait for the money, which I again don't want to send in advance. If he finds another buyer, who would pay for the bird earlier, it is gone.
Still, though, we continue to look for a straight tail 172. :)
 
German guy said:
:yes:

I just spoke with the seller, the earliest pick-up date I could make was too late for him and he doesn't want to wait for the money, which I again don't want to send in advance. If he finds another buyer, who would pay for the bird earlier, it is gone.
:)
Click to expand...

Do not let yourself be rushed into an airplane purchase. Repeat after me.....
 
German guy said:
By my understanding the only real disadvantage of the venturi systems is that the gyros only begin to spool up, once the aircraft takes off. In low IFR conditions, the aircraft might therefore enter IMC, before the gyros have reached full rpm and became sufficiently stable. Icing conditions might also freeze them up.

On the other hand, their simplicity makes them pretty bulletproof what is, from what I heard, not necessarily the case with vacuum pumps.

We are planning to use the the aircraft only in very light IMC, like to climb / descend through a ceiling at at least 1,000 ft.

I like the idea with an electric DG.
Click to expand...


ICE!!


That thing ices up now you're in a very fun spot, now you have to exit icing conditions AS your DG and AI are crapping out.

I have VGs on the Stinson I'm selling, if I would have made her a IFR bird I would have put electric gyros in, or vac pumps and keapt the venturis as a retro/backup somehow.

Also the second you think the weather is going to be one thing, it'll be something worse, if I'm not prepared to fly my entire flight IMC, I'm not going IFR.


Ether way if you want IFR on paper, stick with Venturi gyros, if you're actually going to use it for real IFR/IMC work, you're going to need something else.

On something like this, get on eBay and barnstormers, get a deal on a used 430W and electric gyros from some rich dudes "panel upgrade". Probably can get the whole thing done for not much.
 
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timwinters said:
How do you buy an STC that is no longer available, especially if it includes parts (i.e. mounting brackets, etc.)? How does one determine if it's in the public domain?
Click to expand...

I believe it is automatically considered public domain when the STC or any Type Certificate holder either dies or goes out of business with no clear passing of the torch.

When that happens, the FAA considers the certificate 'public domain'. BUT, here's the kicker....even when that happens, they won't release the data that they hold because it is considered 'proprietary'. So, the best you can do in such a situation is find someone who has the info from a previous and use it as a basis for a 337.

One of the interesting things I learned about WACO.....they fell into this hole. When WACO closed down, they simply stopped doing business. They weren't bought out or merged, so all the WACO type certificates were released to public domain. But, unlike other manufacturers, the senior leadership of WACO gave their entire archives to the Smithsonian, so all of that data is readily available to those trying to maintain/restore old planes like mine.
 
jesse said:
If it were me I'd go electric DG and attitude and leave the Venturi attitude.
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That's a very expensive solution, although if one has the money to put a 650 in the plane, I suppose spending another $5K to add two electric gyros may not be out of reach. But I'm thinking that panel is going to get pretty crowded with two attitude indicators in addition to the other five required instruments plus a couple of CDI's.
 
How would the cost of installing an Aspen PFD compare to replacing gyros and installing a pump?
 
NoHeat said:
How would the cost of installing an Aspen PFD compare to replacing gyros and installing a pump?
Click to expand...
IIRC, an Aspen PFD is around $12K installed.

OTOH, I'm guessing it would cost under $1000 to install a vacuum pump to drive the existing vacuum AI/HI instruments. Only extra cost might be putting in an electric T&B/TC if the existing one is vacuum-driven off a third venturi, but I'm thinking you'd still be in the $2000 range for all of that. Even if you needed to buy new AI/HI because the old ones were dead, that would still be only about $2000 for both, so I'm thinking the very worst case would be about $5K.

But on the third hand, if you're putting in a 650, it's going to play very will with an Aspen, and you can leave the venturi-driven AI as your back-up instrument, and you're going to love what you get with that package.
 
German guy said:
My question is whether I have overlooked something and if somebody else has also gone through the process of having his (straight tail) 172 certified? I believe that all 172s are certifiable, but don't know how to check on this - can I look this somewhere up?
Click to expand...

If somebody will tell me the chapter and verse to "certify" an aircraft for IFR then we can answer your question. Don't wait too long for an answer or you will be very old when you get it.

Jim
 
Ron, I think you missed that it's questionable whether a vacuum pump can be installed in the first place.
 
weirdjim said:
If somebody will tell me the chapter and verse to "certify" an aircraft for IFR then we can answer your question. Don't wait too long for an answer or you will be very old when you get it.
Click to expand...
Actually, there is a place to get the answer to that question -- right here, from the FAA. You will note that there is no operating limitation regarding IFR operations in that document for any of the straight-tail versions. So, there being no limitation, IFR is legal as long as you comply with all the regulations on point (primarily 91.205(d) and 91.411).
 
timwinters said:
Ron, I think you missed that it's questionable whether a vacuum pump can be installed in the first place.
Click to expand...
Well, if a vacuum pump can't be installed, you can go with electric AI/HI instruments and leave the venturi AI as your independently powered backup gyro (see AC 91-75). I believe that will be only about half the cost of the Aspen.

But the Aspen is still nicer. :wink2:
 
frfly172 said:
Diamonds can't be certified ,because they are composite,and have no metal embedded in the skin.
Click to expand...


OK, I read the Avweb article, I read the embedded link in the article, and I did a cursory exam of 14CFR23. Here are the pertinent sections:

23.867 Electrical bonding and protection against lightning and static electricity.

(a) The airplane must be protected against catastrophic effects from lightning.
(b) For metallic components, compliance with paragraph (a) of this section may be shown by—
(1) Bonding the components properly to the airframe; or
(2) Designing the components so that a strike will not endanger the airplane.
(c) For nonmetallic components, compliance with paragraph (a) of this section may be shown by—
(1) Designing the components to minimize the effect of a strike; or
(2) Incorporating acceptable means of diverting the resulting electrical current so as not to endanger the airplane.



§23.1306 Electrical and electronic system lightning protection.

(a) Each electrical and electronic system that performs a function, for which failure would prevent the continued safe flight and landing of the airplane, must be designed and installed so that—
(1) The function is not adversely affected during and after the time the airplane is exposed to lightning; and
(2) The system automatically recovers normal operation of that function in a timely manner after the airplane is exposed to lightning.
(b) For airplanes approved for instrument flight rules operation, each electrical and electronic system that performs a function, for which failure would reduce the capability of the airplane or the ability of the flightcrew to respond to an adverse operating condition, must be designed and installed so that the function recovers normal operation in a timely manner after the airplane is exposed to lightning.




Now, somebody is going to have to tell me, in terms any competent History major can understand, why the Diamond can not be flown IFR. To those who say that a fiberglass airplane is any more susceptible to lightning strike destroying all the electronics on the airplane than a metal ship, I say a profound and enthusiastic ... el toro caca.


So, please educate me. Why do these two sections of the certification rules keep the Diamond from flying IFR?


THanks,


Jim
 
weirdjim said:
OK, I read the Avweb article, I read the embedded link in the article, and I did a cursory exam of 14CFR23. Here are the pertinent sections:

23.867 Electrical bonding and protection against lightning and static electricity.

(a) The airplane must be protected against catastrophic effects from lightning.
(b) For metallic components, compliance with paragraph (a) of this section may be shown by—
(1) Bonding the components properly to the airframe; or
(2) Designing the components so that a strike will not endanger the airplane.
(c) For nonmetallic components, compliance with paragraph (a) of this section may be shown by—
(1) Designing the components to minimize the effect of a strike; or
(2) Incorporating acceptable means of diverting the resulting electrical current so as not to endanger the airplane.



§23.1306 Electrical and electronic system lightning protection.

(a) Each electrical and electronic system that performs a function, for which failure would prevent the continued safe flight and landing of the airplane, must be designed and installed so that—
(1) The function is not adversely affected during and after the time the airplane is exposed to lightning; and
(2) The system automatically recovers normal operation of that function in a timely manner after the airplane is exposed to lightning.
(b) For airplanes approved for instrument flight rules operation, each electrical and electronic system that performs a function, for which failure would reduce the capability of the airplane or the ability of the flightcrew to respond to an adverse operating condition, must be designed and installed so that the function recovers normal operation in a timely manner after the airplane is exposed to lightning.




Now, somebody is going to have to tell me, in terms any competent History major can understand, why the Diamond can not be flown IFR. To those who say that a fiberglass airplane is any more susceptible to lightning strike destroying all the electronics on the airplane than a metal ship, I say a profound and enthusiastic ... el toro caca.


So, please educate me. Why do these two sections of the certification rules keep the Diamond from flying IFR?


THanks,


Jim
Click to expand...


We're not talking about all Diamonds just the DA-20. As to why you can't make it IFR as an owner it's because the operating limitations state VMC only. So unless you can get that limitation removed, you're hosed.

As to why that's there it's because Diamond did not comply with the regulation you posted above which states there must be a means to divert the electircal current from the strike. With the DA-40 they achieved that by embedding metal strips in the composite airplane that would direct the energy from the strike. Diamond did not bother to do that in the 20 which is why it's a limitation.

As to why they didn't bother, I personally suspect they did it to encourage people to upgrade to the 40.
 
Jim, it's not about destroying the electrical equipment, it's about blowing a big hole in the wing and crashing.
 
JHW said:
Jim, it's not about destroying the electrical equipment, it's about blowing a big hole in the wing and crashing.
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Sorry, I don't buy that. What is the difference between blowing a hole in the wing VFR or IFR?

Jim
 
:wink2:
weirdjim said:
Sorry, I don't buy that. What is the difference between blowing a hole in the wing VFR or IFR?

Jim
Click to expand...
Standards require you protect for lightning strikes if the plane will be in IMC and require no such requirement it it's VMC only.

Could you get struck by lightning in VMC? Probably. But they consider it a low enough risk that you don't need any engineering data to say nothing bad will happen if it does get struck.
 
weirdjim said:
Sorry, I don't buy that. What is the difference between blowing a hole in the wing VFR or IFR?

Jim
Click to expand...
not a darn thing. Which might give you pause if considering skimming the bottom of some CB in that plane VFR
 
Lightning isn't the big issue here -- static electricity is, and when you fly through a cloud, you pick up a static electric charge even if you stay out of the convective activity necessary for lighting. Hence, the limitations on the placards shown in the DA20 POH pages 2-13 et seq., stating day/night VFR only and flight in VMC only. Note that Flight Standards says you can still fly a DA20 (or any other aircraft not certified for IFR) under IFR for instrument rating training and practical tests only if you stay in VMC, but 91.205(d) and 91.411 must still be complied with. That is also why some planes have static discharge wicks and specified minimum numbers of those wicks to fly in the clouds.
 
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German guy said:
My wife and I are just about to buy a 1957 straight tail 172 (venturi vacuum). We would also like to use it for (light) IFR. I am aware of the advantages / disadvantages of a venturi driven vacuum system and also read quite a bit about this topic in the Cessna 170 forum, were a number of pilots had their 170s IFR certified.

This is what 91.205(d) requires for IFR flight:

(d) Instrument flight rules. For IFR flight, the following instruments and equipment are required:

(1) Instruments and equipment specified in paragraph (b) of this section, and, for night flight, instruments and equipment specified in paragraph (c) of this section.
(2) Two-way radio communication and navigation equipment suitable for the route to be flown.
(3) Gyroscopic rate-of-turn indicator [...]
(4) Slip-skid indicator.
(5) Sensitive altimeter adjustable for barometric pressure.
(6) A clock displaying hours, minutes, and seconds with a sweep-second pointer or digital presentation.
(7) Generator or alternator of adequate capacity.
(8) Gyroscopic pitch and bank indicator (artificial horizon).
(9) Gyroscopic direction indicator (directional gyro or equivalent).

The airplane we are interested in has all of this, assuming a successful pitot / static check.
The only thing which is missing is the 'navigation equipment suitable for the route to be flown.' We are planning to install a Garmin GNS 650, so that this requirement would also be met.

My question is whether I have overlooked something and if somebody else has also gone through the process of having his (straight tail) 172 certified? I believe that all 172s are certifiable, but don't know how to check on this - can I look this somewhere up?
Click to expand...

If you're putting in a 650, put in an Aspen or G-500 as well, now you have capability without adding a vacuum pump.
 
Henning said:
If you're putting in a 650, put in an Aspen or G-500 as well, now you have capability without adding a vacuum pump.
Click to expand...
Adding a G500 display system is about twice as expensive as adding an Aspen PFD. I've flown with both, and if money were no object, I'd put the G500 in my Tiger, but choose wisely -- you can probably find a lot better things to do for your airplane with that extra $12K or so.
 
Ron Levy said:
Adding a G500 display system is about twice as expensive as adding an Aspen PFD. I've flown with both, and if money were no object, I'd put the G500 in my Tiger, but choose wisely -- you can probably find a lot better things to do for your airplane with that extra $12K or so.
Click to expand...

Really? For flying IFR? What?:dunno: I wouldn't have spent the money if I didn't see the extraordinary value flying Av's Comanche.
 
You guys are advocating that this guy spend $50k on a $25k airplane!

:rofl:

Oh...don't forget the auto pilot!
 
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