2-2  UNCONTROLLED COPY WHEN DOWNLOADED  Check with FSIMS to verify current version before using  back pressure is gradually reduced until the airplane is climbing at a normal angle with the  banner in tow.  The approach to the pickup masts should be flown appropriate to the performance characteristics  of the aircraft. Care must be taken to avoid snagging the towline with the airframe. An approach  that is both too low and too slow may result in the grapple hook bouncing off the ground. The  length of the grapple hook and line assembly should be limited to a length that will not allow the  hook to strike the cockpit area of the airplane if it should come up over the fuselage. Grapples  contacting a hard surface have been known to bounce upward and forward, over the airplane,  snarling the horizontal stabilizer or a wing.  Stalls during the banner pickup procedure constitute one of the more frequent causes of banner  towing operational accidents. A stall occurs when an airfoil reaches a critical angle of attack  (AOA) and is a function of wing loading, independent of airspeed. In fact, an excessively abrupt  rotation of an airplane during a pickup, or a snap or steep turn after a missed pickup, may be  sufficient to precipitate an accelerated stall.  Note: The formula for a stall is the square root of the load factor multiplied by  the normal stall speed. Gradually reducing back pressure while in the climb as the  banner is picked up increases the margin from the stall threshold by decreasing  the wing loading and consequently the AOA.  FLYING WITH A BANNER IN TOW.  The accidental release of a banner in flight may not be  hazardous to the tow plane or crew, but it may pose a threat to people and property on the  surface. Banner towlines should be examined carefully for flaws before each towing day.  Grapple hooks should also be examined for cleanliness and smoothness. Any surface  irregularities on a hook can act as an abrasive and degrade the towline loop during the pickup as  the line moves laterally over the hook while tension on the line is increased. Whenever possible,  banner material and lines should be of nonconductive material; this reduces the risk of shorting  out powerlines in the case where a banner is released over powerlines by accident.  LANDING WITH A BANNER IN TOW.  Should a malfunction make it impossible to release  the banner, it is generally uneventful if a hard surface runway is used. However, a special  technique can be used if the landing is attempted on a sod or dirt runway. If the masthead and  banner lay down on the sod runway, each blade of grass folds over the mast and each individual  letter pole on lettered banners causes drag. The pilot needs to be aware that the masthead may  dig into the soft turf like an anchor, stretching the towline, and sometimes breaking it. If the  towline breaks, the sudden release of energy will cause the airplane to pitch down and a  nose-over condition may occur. This condition can be countered by maintaining back pressure  on the flight controls and adding full power once the drag caused by the masthead is  experienced. After the airplane is again stabilized, the power is reduced.  MULTIPLE TOW HITCHES.  When multiple tow hitches are used, an airplane may tow a  succession of banners without having to land and reinstall a grapple line after every drop. A bank  of as many as four or five tow hitches may be installed on the aircraft, and a grapple line is  affixed to each. These lines are stowed within reach of the pilot in the same manner as previously  discussed. Care must be taken to prevent multiple lines from tangling, and since the pilot will be 