Stream following mode of operation


  The alpha-mode of biangular handling of the liftoplane requires having a steady reference frame of entire aircraft relative to airstream. In particular, condition of the requirement is simple “keep nose against airstream”, having the horizontal axis of the fuselage parallel to the airstream exactly. So I reference the feature as “stream following mode” of operation or simple stream following.


  The mode of operation is supported by a system having two principal elements: some kind of actuator for performing the corrective actions and some element for detect a deviation of the airstream. For the first I use stabilators. And for second I use a Stream Deviation Tube SDT, which is new kind of pneumatic tube. Both elements act in a common negative feedback loop of the system.


  The rotors induce a high moment on entire aircraft. I reference it as Moment Ratio (MR) defined as I explained in the topic about cyclorotor aircrafts. For many operations its value lays in a range from 0.2 to 0.7, but for the high-speed flight it can be higher than 0.85. A part of the MR value is compensated by weights of pilot and passenger, and by adjusting placement of racks for accumulators. But significant value is still remained for the high MR. So stabilators have enough area for provide a force enough for compensate it. The some high area requires having of precision articulation of the pitch for these stabilators. I use worm gear for the articulation as it pictured on the chart below.

Steering of stabilator

  There the worm gear is fixed on a shaft, which is common for both stabilators. Rotation of the gear by the worm originates through a universal joint from the cockpit direction.


  The SDT is placed on the center of nose of fuselage, as it shown on the image below.


Nose view and the SDT

  Forward side of the SDT has two equal slopes, where one looks to up and other looks to down, having about 40 degrees each from horizontal plan. Each of these slopes has a beginning of an entry channel, drilled on its center normally to its surface. In the beginnings of these channels dynamic pressures are developed, when the SDT encounters an airstream. These pressures are propagating through interior of the SDT toward cockpit, like as it occurs for the Pitot-static tube (PST), which is observed above the SDT on the image. These output pressures of both tubes act on respective electrical sensors and on respective pneumatic indicators. For these SDT pressures a special Stream Deviation Indicator SDI exists as part of the cockpit’s instrumentation. It is pictured below.


Stream Deviation Indicator SDI

  The SDT also has electrical heaters inside, against an icing. Additionally, construction of it has an anti-clogging drainage system, providing high reliability.


  Control of pitch of the stabilators is performed by a special Stabilator Pitch trimmer (SP-trimmer), which is also part of the cockpit’s instrumentation. Manual control of the trimmer together with using the SDI services only emergence cases. Normally, the trimmer is under an automatic control. A special servo is mechanically connected to the trimmer, which is also connected to a special encoder. A special stabilator controller manages the trimmer trough the servo, using a feedback from these electrical sensors, adjusted by a low-pass filter. The encoder reports its value to a central computer. A bi-directional connection between the stabilator controller and the central computer permits to apply more sophisticated management for the stabilator controller from side of the central computer upon reusing propagated values of pressures from the electrical sensors. Also value from the encoder is used by the stabilator controller as feedback against its operating outside of operational margins of stabilators.


Copyright © 2018 Yuri Feldman - All Rights Reserved