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#11
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need for dial altimeter?
Transponders give Flight Level (assuming they are working properly), so
will give the altitude ATC are intereted in. That's how they know what FL you are at when not talking to them. At 12:52 26 September 2008, John Smith wrote: JJ Sinclair wrote: On the last home-built I regestered, the federallies required a mechanical airspeed, altimeter and compass........nothing else. But I have observed that the panel I am now flying has altitude displayed all over the place, in two GPS's, in the SN-10 and in the transponder. The large altimeter takes up a lot of space and provides the least important info..........................we can all estimate our altitude for landing, can't we? The rest of the time its just nice to know info. Except when you're flying in the among controlled airspace, where neither GPS altitude (geometric) nor transponder altitude (QNE) do you any good. Loggers usually can give you QNH altitude, provided you set them correctly and your battery isn't flat. |
#12
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need for dial altimeter?
Peter Purdie wrote:
The large altimeter takes up a lot of space and provides the least important info..........................we can all estimate our altitude for landing, can't we? The rest of the time its just nice to know info. Except when you're flying in the among controlled airspace, where neither GPS altitude (geometric) nor transponder altitude (QNE) do you any good. Loggers usually can give you QNH altitude, provided you set them correctly and your battery isn't flat. Transponders give Flight Level (assuming they are working properly), so will give the altitude ATC are intereted in. That's how they know what FL you are at when not talking to them. The pilot still needs to know msl altitude, because that's how the airspace is designated at 18,000' and below in the USA. Also, elevations (airports, mountains, obstructions, etc) use msl, and other gliders and aircraft will report their altitudes in msl. -- Eric Greenwell - Washington State, USA * Change "netto" to "net" to email me directly * Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4 * New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more * "A Guide to Self-launching Sailplane Operation" at www.motorglider.org |
#13
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need for dial altimeter?
On Sep 26, 7:52*am, Peter Purdie wrote:
Transponders give Flight Level (assuming they are working properly), so will give the altitude ATC are intereted in. *That's how they know what FL you are at when not talking to them. The controller see your transponder altitude CORRECTED for the local pressure. So don't give them the number off the transponder display unless the current pressure is 29.92 That's why the altimeter must be calibrated when you calibrate the transponder. You must be able to set the altimeter to the current (not what it was several hours or hundreds of miles away) before talking to ATC, and that is why they will give you an altimeter setting on initial contact unless you indicate you have current ATIS info. -Tom |
#14
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need for dial altimeter?
"TXBill" wrote in message . .. Wouldn't a glass-cockpit soaring instrument, say something like the new ClearNav from NK, provide even better situational awareness if it had an airspeed strip down the right edge and an altitude strip down the left edge? How about adding "altitude required for next waypoint" and "speed to fly" indicators to those strips? I'd sure like to have them....but, then, I'd like to have a horizon, too. And a G-meter strip next to the airspeed strip. Oh, and how about a vario strip next to the altitude strip? With real-time and average indicators? Maybe a voltmeter? A compass? Synthetic 3D terrain view? Thermal markers? What else do y'all think might be useful? Sounds like a whole new class of instrument, an "ESIS" or "Electronic Soaring Information System". Put all that on a 12inch-diagonal daylight visible screen and the only "steam guages" I'd have in the cockpit would be a compass and 57mm airspeed indicator. Just in case. Hmm, sounds like an idea for a future "Soaring Tech" article..... See you on the porch, - Bill All well an' good, but to gain wide acceptance it needs to be energy efficient with battery back-up for at least 5 hours on two AA cells. bumper zz Minden |
#15
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need for dial altimeter?
Peter Purdie wrote:
Transponders give Flight Level (assuming they are working properly), so will give the altitude ATC are intereted in. That's how they know what FL you are at when not talking to them. There are places in the world where airspace structure is pretty complex and where you must know your QNH altitude to stay clear of airspaces, regardless of ATC. |
#16
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need for dial altimeter?
On Sep 26, 9:43*am, 5Z wrote:
On Sep 26, 7:52*am, Peter Purdie wrote: Transponders give Flight Level (assuming they are working properly), so will give the altitude ATC are intereted in. *That's how they know what FL you are at when not talking to them. The controller see your transponder altitude CORRECTED for the local pressure. *So don't give them the number off the transponder display unless the current pressure is 29.92 That's why the altimeter must be calibrated when you calibrate the transponder. *You must be able to set the altimeter to the current (not what it was several hours or hundreds of miles away) before talking to ATC, and that is why they will give you an altimeter setting on initial contact unless you indicate you have current ATIS info. -Tom Actually this is a common misconception, (one of several reported recently in the Safety Corner in Soaring magazine). The encoder/ transponder/altimeter system is checked as a part of an install and you must also do this if the static system is touched during maintenance. Subsequent checks for aircraft operating VFR are only required to test the transponder RF/signal properties and do not need to check the altitude calibration. IFR calibration do. See FAR 91.413 appendix F (RF/signal properties only) and Appendix E (install/static maintenance and IFR checks). Back to the original question, I would not want to fly any aircraft without the ability to reliably (i.e. when the battery dies) know and be able to report pressure altitude. Darryl |
#17
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need for dial altimeter?
Back to the original question, I would not want to fly any aircraft without the ability to reliably (i.e. when the battery dies) know and be able to report pressure altitude. Darryl If your battery dies, wouldn't you lose your ability to report anything to anybody? I'm not suggesting we fly around without an altitude readout of some kind, but does it have to be the big, old 80mm round dial? Why can't I use the pressure altitude displayed in double height on the home page of my SN-10. Keep the black cursor on it, so my altitude can be read at a glance. If I should have the SN-10 on another page, I can always read pressure altitude to the nearest 100 feet off my transponder. If for some reason I'm unable to use any of the above, I can always read pressure altitude off the GPS (model 20). Most of us have two batteries so we can switch if the primary goes dead. JJ |
#18
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need for dial altimeter?
JJ Sinclair wrote:
I'm not suggesting we fly around without an altitude readout of some kind, but does it have to be the big, old 80mm round dial? Why can't I No it hasn't to be 80mm, mine is 57mm. Aside from this, yes it has to: More than once I was happy to be able to continue my flight under a class C ceiling despite of two flat batteries. Besides, many contries reqire gliders to be equipped with a certificated altimeter. |
#19
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need for dial altimeter?
On Sep 27, 7:51*am, JJ Sinclair wrote:
Back to the original question, I would not want to fly any aircraft without the ability to reliably (i.e. when the battery dies) know and be able to report pressure altitude. Darryl If your battery dies, wouldn't you lose your ability to report anything to anybody? I'm not suggesting we fly around without an altitude readout of some kind, but does it have to be the big, old 80mm round dial? Why can't I use the pressure altitude displayed in double height on the home page of my SN-10. Keep the black cursor on it, so my altitude can be read at a glance. If I should have the SN-10 on another page, I can always read pressure altitude to the nearest 100 feet off my transponder. If for some reason I'm unable to use any of the above, I can always read pressure altitude off the GPS (model 20). Most of us have two batteries so we can switch if the primary goes dead. JJ Yes, assuming the backup handheld dies as well, then I'd just be talking to myself. I fly a certified glider so I have no choice but to follow the equipment list. You tell us J.J. what is the requirements for homebuilt/experimental and racing/exhibition/experimental. Darryl |
#20
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need for dial altimeter?
I fly a certified glider so I have no choice but to follow the equipment list. You tell us J.J. what is the requirements for homebuilt/experimental and racing/exhibition/experimental. Darryl Alas, yes they both require old fashioned dial altimiters. With todays glass cockpits, I'm wondering if this requirement isn't outdated? JJ |
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