esac (01/20/83)
I'm only a new private pilot (95 hours) but I'm already thinking about an instrument rating. I read with some interest previous discussions about the loss of this or that during an instrument flight and had a few thoughts I'd like to pass along. On the subject of lost comm procedures, its true that a hand held 720 is mighty expensive insurance against a low probability failure. But why does it have to be a 720 channel transceiver. For about $300 one can get a 4-channel transmitter that will probably do the job. All you will probably need in an emergency situation is 121.5. Correct me if I'm wrong but I think you should be able to get a DF steer with an item such as I've described. If you shop carefully or are willing and able to do your own radio work, you can probably even beat $300.. Another item you might want to consider is a skydiver's altimeter. The one I have is made by Steve Snyder Enterprises (SSE) of Pennsauken, NJ. Its cost is about $95 at the present time. True, it's not as accurate as a standard aircraft altimeter, but if you get a good one, they're pretty damn close from 5 grand on down. And it can't accurately be corrected for changing altimeter settings but it's better than nothing at all (isn't it?). The last item would be to get ahold of your friendly neighborhood CFII from time to time to make sure your partial panel procedures are up to snuff. Hope someone finds this worthwhile.
avsdS:avsdT:roberts (01/21/83)
While it's true that a simple radio might get you in touch with the F.S.S., you may not be able to get a DF steer. Not all F.S.S facilities have this capability. Also, in mountinous terrain the only ones who might be able to hear you are the Center boys. If you could contact a F.S.S. that does not have DF steering capabilities and only had a four channel hand held, they would have to maintain a secondary conversation with Center (who would hopefully be able to have your painted radar blip identified), and communicate steering information to you second hand. Not a nice way to go.
danny (01/26/83)
Having nothing but 121.5 capability in an IFR emergency situation is even more useful than has been pointed out on the net. Perhaps more important than the many ground facilities that monitor 121.5 are the large number of airline and gen. av. pilots who make a point of "guarding" 121.5 on an otherwise unused radio and can relay emergency messages to a ground facility on an appropriate frequency. This can be quite significant since VHF air-air range can easily be a couple of hundred miles. As for an inexpensive back-up altimeter, you can do better than the $95 skydiver model. I've seen altimeters meant for auto dashboards that sell for $16 and should be accurate to within several hundred feet. Not the kind of thing you'd wanna use for a non-precision approach to minimums, but better than nothing at all.
cfiaime (01/26/83)
Question: Has anyone out there in "Netland" ever had an altimeter
failure with a properly maintained unit? (The one in my Funk was
useless until it was rebuilt, but that was not PROPERLY maintained.)
The point is, a skydiver altimeter, an auto altimeter are not meant
for use in aircraft at all. Do you wish to vent this unit to the cabin?
Or do you wish to install it with a seperate static source?
If you really wish a backup altimeter, many instrument shops have good
used units for under $100 (see Trade-A-Plane).
Lets review the FARs for a moment concerning the altimeter. First, it
is required for VFR (and IFR) flight as per FAR 91 something. But,
while flying VFR, if the altimeter breaks (and they dont break catastrophicaly)
the pilot still has the ground in sight and can still fly without reference
to the altimeter. Hence, in VFR, and altimeter failure is not an
emergency. For IFR flight, the altimeter is inspected every two years.
The only way for an altimeter to fail is:
1) the diaphram ruptures
2) various gears and screws internally loosen
3) the case ruptures
4) the static system malfunctions.
In the first two cases, the biennial check of the unit will show if there
is a developing problem. In the third case, you have more problems than
just an altimeter problem. In the last case, an alternate static source
keeps the altimeter working.
Some encoding altimeters WILL fail if the electrical system malfunctions.
The Cessna 300 series encoder is like this. If you notice, the aircraft
with the Cessna 300 series encoding altimetter installed also have a
normal barometric altimeter installed in the panel. (This is a certification
item for the use of the Cessna 300 encoder, by the way.)
So, for my money, the altimeter will be backed up by having an alternate
static source only, not a skydiver or auto altimeter. However, this is
only my opinion, so don't take it as the Gospel.
Jeff Williams
BTL - Indian Hilldanny (01/26/83)
I certainly agree with Jeff Williams that altimeter failure in flight is not likely (tho I've read about a cupla such incidents). There are several radios/instruments that I would give higher priority to as far as back-ups for IFR flight are concerned. However it is a fact that the altimeter is probably the simplest and cheapest to back up. And considering that we're only talking about accuracy to within a few hundred feet, venting into the cabin is no problem (and having passed the instrument written, we know in which direction it'll be off, right?). I've flown with an (aircraft-type) altimeter sitting in my lap not connected to anything and it agreed with the panel-mounted static-port-vented instrument within about 100 ft. Imagine flying a C172-type aircraft in IMC in an area of 5000' peaks and sufferinf an altimeter failure. Having a back-up that told you your altitude to even within a THOUSAND feet would be highly welcome. (Cabin-venting of course assumes an unpressurized cabin.)