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#71
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"mah" wrote in message ... Rich Ahrens wrote: Yes, those static ports are pretty unreliable! :-) All those moving parts... Yep, I've got a can of static port grease on the shelf next to my bottle of horn fluid and the box of muffler bearings. Well the only tiny grain of truth in that statement is that a static port can be occluded by a foreign object. On the ground this can be something like an insect setting up housekeeping in it, in flight ice is probably the biggest risk factor. Since loss of the static port will bugger up 3 basic flight instruments (altimeter, ASI and VSI) this is non-trivial. The CO |
#72
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"Gord Beaman" ) wrote in message . ..
mah wrote: Tarver Engineering wrote: The sole reason for using a static port is so the guts can be removed from the pitot tube, in order to improve reliability. A pitot port produces no static pressure datum. Just as an example, when the aircraft is sitting still on the ground - airspeed = 0. Since the pitot and static ports are in the same state, doesn't that imply that static pressure is present at the pitot port? MAH Sure it's there, but it's there only until the a/c starts to move. It's then no longer 'static pressure' because it's been raised by the ram effect of the movement. That's why you now need a 'static port' to supply the static pressure to use as a reference. Is it really that difficult to see?!? where are the mud bees? |
#73
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"The CO" wrote in
: Well the only tiny grain of truth in that statement is that a static port can be occluded by a foreign object. On the ground this can be something like an insect setting up housekeeping in it, in flight ice is probably the biggest risk factor. Since loss of the static port will bugger up 3 basic flight instruments (altimeter, ASI and VSI) this is non-trivial. Or masking tape left in place after maintenance. At least one airliner has crashed because of this. Many fatalities. -- Regards, Stan |
#74
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(running with scissors)
Date: 3/2/2004 5:18 PM Central Standard Time Message-id: "Gord Beaman" ) wrote in message ... mah wrote: Tarver Engineering wrote: The sole reason for using a static port is so the guts can be removed from the pitot tube, in order to improve reliability. A pitot port produces no static pressure datum. Just as an example, when the aircraft is sitting still on the ground - airspeed = 0. Since the pitot and static ports are in the same state, doesn't that imply that static pressure is present at the pitot port? MAH Sure it's there, but it's there only until the a/c starts to move. It's then no longer 'static pressure' because it's been raised by the ram effect of the movement. That's why you now need a 'static port' to supply the static pressure to use as a reference. Is it really that difficult to see?!? where are the mud bees? Shacking up in the pitot tubes. Dan, U.S. Air Force, retired |
#75
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Can you point to a reg tht says that? I don't think it is true. Mine was
IFR certified when I bought it, and it did not have alternate static (I've since added it). Also the FAA materials for the IFR written mention several times that breaking the VSI glass is the way to get alternate static on an airplane that doesn't have a valve. I wouldn't think they'd make such a big deal about it if an alternate static source was requried for IFR cert. The CO wrote: IIRC in fact, for an aircraft to be certified for IFR it has to have an alternate static source *as well*. -- --Ray Andraka, P.E. President, the Andraka Consulting Group, Inc. 401/884-7930 Fax 401/884-7950 http://www.andraka.com "They that give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -Benjamin Franklin, 1759 |
#76
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"The CO" wrote in message = ... =20 =20 Well the only tiny grain of truth in that statement is that a static port can be occluded by a foreign object. On the ground this can be something like an insect setting up housekeeping in it, in flight ice is probably the biggest risk factor. Since loss = of the static port will bugger up 3 basic flight instruments (altimeter, ASI and VSI) this is = non-trivial. =20 The CO =20 =20 Well, let me tell you of the time my airplane was released from an = annual inspection with the static line open to the air in my pressurized cabin. Since I'm cautious, I'd waited for MVFR conditions before launching. My cabin began to pressurize just as I entered the base of the stratus, and my rate of climb suddenly showed zero, among other annoying signs. I continued my climb by maintaining attitude until I popped out on top, and asked for an ILS approach and return for landing. An airliner ahead of me called out the tops of the clouds, so I had a pretty good idea of my altitude before intercepting the ILS. If I hadn't been so close to the airport, I'd probably have thought = about dumping pressurization to see if the altimetry would come back, but in this case it was easy just to return and let the mechanic re-connect the hose. He was pretty embarrassed. ---JRC--- |
#77
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Ray Andraka wrote:
Also the FAA materials for the IFR written mention several times that breaking the VSI glass is the way to get alternate static on an airplane that doesn't have a valve. I wouldn't think they'd make such a big deal about it if an alternate static source was requried for IFR cert. It should be mentioned here that this trick only works on an unpressurized a/c. You won't get much activity on the VSI needle if you try this with a pressurized aircraft!. -- -Gord. |
#79
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"Ray Andraka" wrote in message ... Can you point to a reg tht says that? I don't think it is true. Mine was IFR certified when I bought it, and it did not have alternate static (I've since added it). Also the FAA materials for the IFR written mention several times that breaking the VSI glass is the way to get alternate static on an airplane that doesn't have a valve. That might work if the cabin was unpressurised, depends on whether the guage face was vented to the static side of the pressure balance. I wouldn't think they'd make such a big deal about it if an alternate static source was requried for IFR cert. Ah, in Australia mate. I can't quote the ANO/R off the top of my head but to be certified for Class 1 it needs an alternate static source IIRC. I'll see if I can find the ANO/R somewhere. (ANO= Air Navigation Order ANR= Air Navigation Regulation) I can't speak for the FAA, so if they don't require alternate static source for Class 1 IFR I'm rather surprised, but I guess it could be the case, I don't know. Class 4 IFR (NVMC) doesn't require it in Oz. The CO |
#80
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