789
edits
Zeppelin NT: Difference between revisions
Jump to navigation
Jump to search
→Gas and Envelope: More information on the use of ballonets.
m (→Known problems) |
(→Gas and Envelope: More information on the use of ballonets.) |
||
| Line 39: | Line 39: | ||
* F/f - Open/close the gas valve. | * F/f - Open/close the gas valve. | ||
* Q/q - Inflate/deflate fore ballonet. | * Q/q - Inflate/deflate fore ballonet. | ||
* A/a - Inflate/deflate aft ballonet. | * A/a - Inflate/deflate aft ballonet. | ||
The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume; and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other. | |||
<b>Envelop pressure management</b> | |||
When the airship rises the gas in the envelope expands and consequently the the total volume of the ballonets has to decrease or the envelope pressure will increase. There are pressure relief valves that automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty) but the prudent airship pilot would rather use the manual ballonet valves than rely on the relief valves. | |||
When the airship descends the increasing ambient pressure causes the gas in the envelope to contract and to maintain the envelope pressure above the ambient pressure total volume of the ballonets has to increase. The pilot has to set the ballonet controls for inflation. If the envelope pressure drops too low an alarm will sound. Monitor the gas pressure gauge! | |||
<b>Pitch trim</b> | |||
On the Zeppelin NT pitch trimming is done via the relative fore/aft ballonet inflation rather than with the elevator trim. | |||
To trim towards: | |||
* nose heavy - set the fore ballonet valve for inflation and/or the aft for deflation. | |||
* tail heavy - set the aft ballonet valve for inflation and/or the fore for deflation. | |||
====Ballast==== | ====Ballast==== | ||