CitationJet From United States of America, joined Mar 2003, 2235 posts, RR: 3 Reply 1, posted (1 year 7 months 2 weeks 5 days 2 hours ago) and read 4069 times:
It is called a trailing cone. "Trailing cones (or trailing wires as they are often incorrectly called or trailing static cones), were first developed and tested in the 1950s and 1960's as a simple means of calibrating the static pressure (altitude reporting) error of an aircraft's pitot-static_system. It does this by giving an accurate measurement of the ambient atmospheric pressure (static pressure) well clear of the aircraft's fuselage. The trailing cone system trails generally 1 to 1.5 times the wing span length behind the aircraft via a high-strength pressure tube. Static pressure is measured forward of the cone by several static ports. The cone stabilizes and aligns the ports relative to the freestream airflow."
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 6, posted (1 year 7 months 2 weeks 4 days 17 hours ago) and read 3297 times:
Quoting LTC8K6 (Reply 4): I think they reel it in for takeoffs and landings.
There are fixed and retractable trailing cones...retractables have a winch like what you see in Reply 5.
Fixed cones are strung out behind the aircraft prior to takeoff and then picked up by a vehicle or something similar after landing. Fixed cones are good when you only need it a few times, since they're way simpler to install.
broke From United States of America, joined Apr 2002, 1322 posts, RR: 4 Reply 15, posted (1 year 7 months 2 weeks 3 days 2 hours ago) and read 2564 times:
A carrier I worked for was certifying their L-1011's for RVSM operations. Lockheed was not going to do that for the operator but they did provide us with the information on the installation and use of a trailing cone as part of the project to measure the accuracy of the altitude measurement system.
It turned out that all L-1011's built had provisions for the installation of a trailing cone. We installed one and extended and retracted it manually during the certification flights. It help us to certify the L-1011's for RVSM with surprising little difficulty.