An Additive To Propulsion-Controlled Aircraft

Air Safety Week, Sept 13, 2004

More precise direct control of longitudinal trim and flight path angle - while avoiding undamped phugoids - might be achieved by providing manually operated forward-hinged/outward opening spoiler panels on either side of the nose, suggests ASW contributing editor John Sampson. Such an arrangement would eliminate the lag and long-period oscillations attendant to engine-only pitch control with PCA. The spoilers upon deployment would only have to present to the airflow with a slightly negative angle of attack (or, more correctly, incidence). With appropriate outward pivoting, leverage and actuation, the spoilers could be made a secondary function of beefed-up nosewheel doors (port and starboard). Mounted abeam the instrument panel and operated manually by a handle adjacent to the nose-wheel steering tiller, the panels would more effectively allow thrust differentials to control roll while enabling easier climb, descent, overshoot and landing flare pitch and heading control. Actuation? Lever or cable via pulleys with a 3:1 mechanical advantage and spring-loading. Secondary effects? Roll: none. Yaw: none. Pitch: by symmetrical minor incremental drag increments/decrements. Normally lock-wired closed. Other advantages:

* Pilots would be able to familiarize themselves with control and effectiveness during aircraft conversion and in the simulator.

* The aircraft would remain on its trim speed and would be quite controllable during gear extension.

* Because drag is proportional to speed squared, the effectiveness, sensitivity and predictability of nose-mounted spoilers would be constant over a wide speed range - and approach path pitch control could be accurately graduated (as in a glider's use of spoilers).

* They would be useful for incipient stall avoidance/recovery. Speed getting dangerously low? Then deploy spoilers and the nose drops for recovery (as against "increase thrust and nose naturally rises deeper into the stall").

* They could also be effective in assisting recovery from an unexpectedly adverse center of gravity (or cargo shift) after take-off (or fuel loss in flight) with an operating hydraulic system.

* Electric motor control of the nose-mounted spoilers (both collectively and differentially) would also be possible, thereby helping to accommodate the asymmetric engine scenario.

To take the concept a step further: canard surfaces could provide direct differential roll control and direct collective pitch control (such as the allflying canards on the TU-144 "Concordski," which were extendable/retractable).

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