Citation Spring 2001

• Weather Radar Tilt Management
• Keep Track Of Your Tire Changes
• Technical Tool Tip
• Cycling Firewall Shutoff Valves

Weather Radar Tilt Management

— Jim Wheaton

Storm season is upon us! The technology of radar is a great tool to avoid damaging weather, but it is important to remember its limitations. Radar registers only “wet” objects such as rain, wet hail and wet snow. This excludes “dry” hail, ice crystals and dry snow which are most common at high altitudes. Recently, Duncan Aviation technicians have repaired several aircraft which were flown into damaging “dry” precipitation which was invisible to properly functioning radar systems and alert pilots.

To minimize this possibility, it is imperative that flight crews train, practice and master the use of their radar’s manual tilt function. Some pilots rely on the auto-tilt feature to track cells, but this feature is designed to compensate for aircraft altitude changes only. Instead, the flight crew should manually adjust tilt as the aircraft moves in relation to the storm cell and focus on the most reflective precipitation which is found in the bottom 2/3 of storm cells. Proper tilt management allows radar to see precipitation at lower altitudes and alert the crew to the potential of damaging precipitation at higher altitudes. According to multiple manufacturers’ technical reps, poor tilt management is the leading cause of radar performance complaints.

Keep Track Of Your Tire Changes

— Rick Braun

Citation models 500, 501, 525, 550, 551, S550, 560, 560XL and 650 use BF Goodrich landing gear wheels. The component maintenance manual requires that the paint be removed and a more extensive NDT inspection be performed at every fifth tire change.

Many operators do not keep track of tire changes in their logbooks. If entries are not made, it must then be assumed that the wheels are on their fifth tire change.

The NDT required at the fifth tire change requires more downtime; the wheel must be stripped, NDT’d, painted and then reassembled.

To reduce the downtime and expense associated with these landing gear wheels, Duncan Aviation suggests that operators include records of tire changes in their logbooks.

Technical Tool Tip

— Nick Tykoski & Dave Balling

Hi-lock fasteners are used throughout airframes as high strength fasteners. Some fastener locations make it difficult to get tools in position to properly install fasteners. Snap-On Tool offers a modified ratchet that can install the fasteners. The mod removes the locking ball (for socket retention) and drills a hole through the square drive so that an Allen wretch can be used to hold the fastener while the collar is installed. This creates the problem of having the socket fall off the ratchet when maneuvering the tool to the location of the hilock. The solution is to drill and tap your socket for a set screw. This will secure the socket to the square drive of the ratchet.

Cycling Firewall Shutoff Valves

— Joe Austin

When an airplane arrives for maintenance at Duncan Aviation, an item that is routinely checked is the firewall shut off valves. Duncan Aviation recommends operating both firewall shut off valves once every month or every ten flights.

These valves are critical in an emergency situation, so a routine operational check is crucial.

( Return to top )