Venturi vacuum system for IFR

[Mike Smith]

Carl,

I do have an electric T&B indicator ... good idea. I love the cat and duck idea ... though I'm not sure they would "play" well togather in the cockpit. It might get a little messy. I guess I'll have to keep up my instrument scan. : )

Mike

[GAHorn]

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.

The cat idea works pretty well. And you can tell you're upside-down if he digs his claws into the carpet and his tail sticks straight up. You can also just pick him up and drop him and see which way he twists to land on his feet.
Unfortunately,...the duck idea only works if your airplane is on floats. Wheels don't do well on ponds.

[Kyle]

Just to keep an interesting discussion interesting, what is your collective opinions on the following;

My nav/com is a KX-125 and I do not have a stand alone nav head. This nav com relies on a center window on the radio that serves as the CDI. First step is to tune in the nav freq, then dial in the radial to or from and fly the needle - or the in actuality, the bars left or right of centerline.

The question comes in when your performing a VOR check. Lets say your on deck and performing a test, you tune in the freq and radial, now when you center the needle - what # of degrees was the correction? Two bars, maybe three and what does that actualy represent in degrees? How do you know your within 4 Degrees etc...

I use this radio to fly between vor's and localizer approaches just for fun but if I wanted to do so on an IFR flight plan, how could one record measurable vor checks to satisfy the 30 day requirement?

Regards to all...

[jrenwick]

Kyle,

On a KX125 you can hold down the "Mode" button (I think that's what it's called -- the button right below the CDI display) for a couple of seconds, and it will display the course to the station. With a VOT, it should display 180 degrees To, with the LCD "CDI" centered. Push it again briefly and it switches to 360 From. Anything else -- take the difference between that and what is displayed. I hope I remembered this correctly (I have a 125 in my 170, but it has a remote head and I don't use the LCD much any more).

[Kyle]

John,

If I understand you correctly you mean that first step is to push that button and record its reading which should be the 180, but will actualy read say 178 and then you know its a 2 deg correction (or whatever it comes out to) then another momentary push should give you the 360 reading + or - whatever is displayed ?

[GAHorn]

If you are at a known VOR checkpoint (such as a designated point on the airport that has signage indicating the bearing to/from the station) then centering the CDI and noting the bearing should confirm the calibration/accuracy. (If the sign says it's 134-degrees to the station and your KX125 with a centered needle says it's 139-degrees, then you're out of tolerance.)
Of course, it's a good idea to know the location of your receive antenna and be certain it's located within the center of the circle, if one exists, or otherwise have your aircraft headed directly towards the VOR station. (Close-by VORs can have a degree or so of inaccuracy indicated by sloppy positioning of the aircraft, simply due to the proximity of the station.)

[jrenwick]

John,

If I understand you correctly you mean that first step is to push that button and record its reading which should be the 180, but will actualy read say 178 and then you know its a 2 deg correction (or whatever it comes out to) then another momentary push should give you the 360 reading + or - whatever is displayed ?

Yes, Kyle, I believe that's the way it works. I'm speaking from memory, because I haven't used this feature since June when I started using the remote head exclusively. You have to hold the Mode button down a few seconds to get it to tell you the course to the station. A VOT signal fools the VOR into telling you you're on the 360 degree radial, so your course to the station should be 180 degrees if it's precisely accurate. You can use either the "to" or the "from" indication, as long as you know what you're supposed to be seeing. So if you hold the button down and it says 180, that's zero degrees of error and you don't have to check the radial "from."

There are other ways to check. You could be on the ground at a VOR test site on a known radial, per the A/FD, or you could be on a victor airway and use the radial information off the chart. Either way, you hold the mode button down and then push it again to find the radial value, then note the difference from what it's supposed to be.

John

[Kyle]

Thanks John,

I'm going to the airport after work and give it a try. We have a known bearing from the Provincetown Airport to the Longnook VOR and I'll see what the indications are. If memory serves correctly, ground error is no more than 4 and air checks are 6 degrees. I'll let you know how it does....

Thanks again

[jrenwick]

Kyle,

You probably know this, but the approved methods of checking your VOR are described in FAR 91.171. Here's a link: http://snipurl.com/1rx53. And to be legal for IFR flight, it must be logged per 91.171(d). I keep a small spiral notebook in the glove box for that.

Best Regards,

John

[Kyle]

John,

Thanks, I had that info but not the link. It worked like a champ. While the plane was on deck in Provincetown I tuned in the Longnook VOR with a reading of 129 TO, hitting the mode button it swaped between 128 / 129 TO.

Second touch of the button displayed 308 to 309 FROM. So I know the equipment works well. As far as the recording goes - I have a small book in the plane that I record flight times / oil / gas etc. I'll just enter the VOR checks in the same book as I had done in previous planes.

Thanks again....

[jrenwick]

Cool!

John

[MoonlightVFR]

I just wanted to add a few comments about the effectiveness of venturi vaccuum on take off and landing.

They are marginally effective in takeoff and very little is published or mentioned in ground school. Robert Buck , author of WEATHER FLYING stated it does not spool up until 300-400 ft above ground. Normally there is no reason for avg pilot to even notice.

Years ago I got IFR ticket in my 170 and had problems w venturi system being sluggish on instrument approach. Instructor almost quit me when DG would start wandering at slow approach speed. Installed a fresh Jack & Heintz AN DG and still had same problem. A mature AP/IA advised that we needed MORE VOLUME OF VACCUUM. Easy solution, additional 10" Venturi from a DC-3 and wouldn't you know it the C 170 Manual shows a hook up w two venturi same side of A/C. The amount of suction stays the same, no discernable increase on gage. MORE VOLUME.
It worked. TWO SUCKERS are better than one.

No one wanted me to do IFR with vaccuum venturis. I can almost hear them now , Brashly stating I WANT MORE COWBELL.

You can do it.

regards

[mit]

I have never seen a DC-3 with a venturi.....

[N2255D]

The DC-3's I worked had one. It was on the tail and used to keep the urinal drained.

[blueldr]

If you haven't seen a DC-3 with a venturi, it's just because you didn't start looking at DC-3s soon enough. They started around 1935, you know.
Most people have never seen one with other than a Hydromatic full feathering prop either, but they didn't start out that way.