Venturi vacuum system for IFR

John Clifford · Post by **John Clifford** » Sun May 25, 2003 9:05 pm

The big boys down at the bicycle rack at the airport tell me the an aircraft cannot be certified for IFR operations using a venturi vacuum system. Is this true?

John Clifford
1954 C170B
N2741C

Tom Downey · Post by **Tom Downey** » Sun May 25, 2003 10:58 pm

Mon May 26, 2003 12:23 am

This is a big pet peeve of mine. People boost that their plane is "IFR Certified" like it's a big deal. Ask them what it takes to make an Aircraft "IFR Certified" and I bet they don't know.

The only thing needed to be certified to fly IFR (under Part 91) is the Atimeter, Altitude reporting equipment and static system.
"91.411
(a) No person may operate an airplane, or helicopter, in controlled airspace under IFR unless--
(1) Within the preceding 24 calendar months, each static pressure system, each altimeter instrument, and each automatic pressure altitude reporting system has been tested and inspected and found to comply with appendix E of part 43 of this chapter "

Of course you will need other minimum equipment. That required by 91.205 and 91.503 non of which is required to be certified other than being in operable conditon by the PIC.

91.205 (a) says in part "....., and those instruments and items of equipment are in operable condition."
Note it doesn't say certified.

Further I hear some people say you must have a VOR and a ADF to be "IFR certified". Wrong.

"91.205 (d)(2) Two-way radio communications system and navigational equipment appropriate to the ground facilities to be used."
Notice it doesn't say a VOR and or ADF. In fact you might and I have filed and flown IFR with NO navigation radios. The flights where in the Army with UH-1H's from Navy Willow Grove to Navy Willow Grove for practice GCA approaches. No navigation equipment required Of course we did this under VFR conditions in case we had com radio failure.

So next time someone boosts that their aircrat is "IFR certified" just say, Oh so your altimeter, encoder and static system is working. What other equipment do you have? Then just watch that look you get.

Post by **GAHorn** » Mon May 26, 2003 3:58 pm

Bruce, what you say is almost completely correct.
You actually do have to have some sort of navigational radio appropriate to ground facilities. This means a VOR, ADF, IFR-certified LORAN, etc,....but it doesn't NOT qualify a stand-alone GPS (because it's not a ground facility. This is why some early GPS's required an internal Loran receiver as part of their orginal certification. When the FAA deleted Loran approaches, those early GPS units were no longer mfr'd. and the TSO was changed to accomodate newer GPS's without Loran receivers. These later units meet the rule by being certified as secondary navigational aids.) (The early units still must have their Lorans working to be legal, however.)

Your experience in the Army equipment is because 1) gov't use aircraft do not have to comply with civil equipment requirements (they must comply only with their own authority's requirements, and 2) the VFR conditions for your Army operation was due to official ARMY requirements in civilian airspace.

Do not fall into the trap of interpreting the rule to allow IFR flight without VOR/ADF/LORAN equipment of some sort. Not true. Contact your FSDO for clarification if in doubt. (That's where I got this info.)

Post by **Bruce Fenstermacher** » Mon May 26, 2003 9:49 pm

George, I'm not saying you could find this situation anywhere else. You are correct about military aircraft and operation requirements that may be different than civilian. My point was that way to many people spout of that their plane is "IFR certified" with out a clue what they are saying.

I will bring this up the next time I talk to my FSDO people. But 91.205 says "...equipment appropriate to the ground facilities to be used." Willow Grove at the time had no ground base facilities other than the radar. Today there is a really bad VOR approach no one uses. The flight plans where filed in the civilian system and we were vectored around traffic for Philadelphia. A qualified person could belong to the flying club flying civilian planes from the airfield but they may have been restricted from recovering IFR to the airfield.

The base of operations for the company I currently work for is a little more than half a mile west of the end of 33 at Willow Grove. We have an agreement with Willow Grove to recover our helicopters IFR when returning from a Life Flight so civilians can use the facility with permission.
The FSDO guys are exArmy comrades of mine that flew these approaches with me as instructors. I'm sure when I bring this up our discussions will be lively.

kloz · Post by **kloz** » Tue May 27, 2003 4:28 am

What if the weather is VFR and you have correct charts etc. The ground facilities are the land marks. Or what if you have a panel mounted loran that you can select the VOR waypoint can you fly a VOR approch? You can nav to the VOR with the loran. Do the regs say the Loran has to be IFR to do a VOR approch with it. Is the com/nav radio IFR? I have no ideal the answer to any of this maybe you guys could tell me and tell me where it says any of it is OK.

Post by **GAHorn** » Tue May 27, 2003 11:22 am

kloz wrote:What if the weather is VFR and you have correct charts etc. The ground facilities are the land marks. Or what if you have a panel mounted loran that you can select the VOR waypoint can you fly a VOR approch? You can nav to the VOR with the loran. Do the regs say the Loran has to be IFR to do a VOR approch with it. Is the com/nav radio IFR? I have no ideal the answer to any of this maybe you guys could tell me and tell me where it says any of it is OK.

A VOR approach can only be made with VOR equipment...unless it is a "VOR Overlay" approach such as is becoming common with NDB approaches with GPS overlays. (Hint: there are no VOR/Loran overlay approaches. And technically you cannot navigate to a VOR with a Loran, GPS, or anything else. You can navigate only to a waypoint that coincides with a VOR.) There is no LORAN approach anymore. The FAA deleted them (darn it!) So you can't use a Loran to navigate a VOR approach (no matter how much sense that really makes.) In VFR conditions, while on a flight plan, you still must comply with the rule and have onboard nav radios appropriate to a ground facility. (Example: You intend to fly to Boonies, Tx via Victor Airway 206, which is defined as certain radials between two VORs. Since in the U.S. we use the Victor airway sytem which is defined by VOR's, ...we must have at least one operational, and properly calibrated (and logged within the last 30 days, remember?) VOR receiver onboard,... even if you intend to do your primary navigation referencing some other (secondary) nav system while doing so. In some remote regions, an old "color" airway system may still be in effect,...so an ADF could be used,...but only until the Victor airway system is re-joined. An example is the old "Blue Spruce" route across the No. Atlantic, or the old Blue Airway betwixt Leesville and St. Petersburg. Until you're out over the water between the NDB's making up those portions of the route, you must have a VOR onboard.

russfarris · Post by **russfarris** » Tue May 27, 2003 11:37 am

I heard this nonsense about IFR not being legal with a venturi from a mechanic at a certified repair station. After I showed him the regs, he muttered that the local FAA guy didn't like the idea, as if that had anything to do with it. He may not like the idea, but he can't change the rules.

A properly set up venturi system is perfectly safe and reliable - more so than having a failure prone vaccum pump. I fly my 170 IFR all the time, when the occasion demands it.

The only drawbacks are: 1. The gyros aren't up to speed during takeoff and initial climb, which only affects ops into low ceiling and viz. I personally have about a 700 foot ceiling minumum; after all we are talking about a single-engine airplane here. 2. The possibility of the venturi icing up and reducing the vaccum. If this happens, you are already are in a world of hurt...the amount of ice required to foul up the system also means you are headed for the dirt, IMHO.

A venturi equipped 170 is capable of the same IFR operations as a 172 with similar equipment; i.e. no icing or convective weather.

Now go straighten those guys out (diplomatically, of course!) Russ Farris

sj · Post by sj » Tue May 27, 2003 1:17 pm

Here is a question along this same topic. My 170 is IFR certified with venturis and I have used it for enroute flight, but the gyros do not spool up too well in a climb due to slow speed and not enough vac being generated by the venturis. How do folks deal with this? Do you fly a circuit of the pattern a cruise speed first to get things spinning?

sj

kloz · Post by **kloz** » Tue May 27, 2003 7:18 pm

[

So you can't use a Loran to navigate a VOR approach (no matter how much sense that really makes.) In VFR conditions, while on a flight plan, you still must comply with the rule and have onboard nav radios appropriate to a ground facility

I guess I kind of knew that I was hoping that maybe someone could tell me different.

All goes to Rule #1 when dealing with the Feds. If it makes sence. It's not going to happen.

Post by **GAHorn** » Tue May 27, 2003 9:42 pm

Back to the original question,...
As usual, Russ is correct. The C170 was certified IFR straight out of the factory as long as it had the proper equipment (gyros, venturi, and radios). The only thing added since to the requirement is a "gyroscopic pitch and bank indicator" (art. horizon) and a "gyroscopic direction indicator" (D.G.). (The gyroscopic rate-of-turn (T & B) was always required equipment, and is still unless you have a third horizon that is installed in accordance with 121.305(j) and is usable thru all attitudes, i.e., won't tumble, and is operated independently, etc.)
Check out 91.205, and you'll see that no requirement exists for a vacuum system whatsoever, much less a pump-driven one. Also, contrary to popular belief, notice that a heated pitot is also not required.
But beware! If you operate your 170 above FL 240 you'll also need DME!

So stay out of those summer updrafts.

rudymantel · Post by **rudymantel** » Fri May 30, 2003 1:48 pm

Bruce makes an interesting point with his UH-1 and GCA approaches.
"Navigation radios appropriate to the ground facility..." The only essential navigational radio appropriate to a GCA approach is a com radio !
Rudy

rudymantel · Post by **rudymantel** » Fri May 30, 2003 2:03 pm

Got me to thinking- (always dangerous)
When I got an instrument rating back in 1956 at SAT it was witha low frequency receiver and no gyros, only needle ball and rip cord. (VOR's were already around but mainly for the airlines and corporate guys)

The nav aids were low frequency four-course ranges, A and N signals.
Had to do range orientations and range approaches, high cone, low cone, etc. Without gyros, all turns had to be timed, 3 deg per sec. It wasn't easy, especially in turbulence! When I started to fly with gyros it was SOOO nice !
For what it's worth-
Rudy

Mike Smith · Post by **Mike Smith** » Wed Jun 04, 2003 7:34 pm

Kloz,
I just bought a C-170A and am learning the finer points of venturi vacuum operations. What I have found is that flying a much flatter departure climb profile at a speed of 90 mph (or faster) seems to spin the gyros's up much quicker. If you have a minumum ceiling of 500-800 agl and the gyros have not spun up yet ... level off below the ceiling and wait for the suction gage and instruments to read appropriately. So far this is all just "forward" thinking (read - I haven't done it IFR yet) by a guy trying to figure out how to get into/out of the San Francisco bay area fog layers in the summer time where the ceilings are typically 800-1200 and the tops are usually only 500 to 1000 feet above that. Once outside the immediate bay area it's the typical sunny California day. The catch for me is that I always need to have a "way out". That would be a direction of turn or straight ahead course I could continue until the gyros were operational... or I could RTB. Whatdayathink?

Mike Smith
1950 C-170A

kloz · Post by **kloz** » Thu Jun 05, 2003 4:20 am

Mike
If I have 800 to 1200 ft I just go with that I rarely fly above that anyway.
You have the right ideal with the higher take off / climb speed. You have an electric T&B you could use, also you could take a cat if it stands on the door glass you are in a bank etc. They say a duck works good also when you come in to land and the duck starts flaping flare.