Deep stall recovery system
Aircraft stall can cause catastrophic damage to the aircraft and passengers. Using the standard procedure of stall recovery, aircraft can be recovered from the stall. Take an example of Colgan Air Flight 3407. In 2009, Bombardier Dash-8 Q4000 entered in deep aerodynamic stall during landing approach. This Stall caused 50 fatalities and 4 injuries. Hence to reduce stress on pilot in a case of deep stall, Aircraft Nerds have come up with this system.
How deep stall occurs?
Aircraft Stall is a condition when an airflow detaches from the aircraft wing. Flow separation results in loss of lift and aircraft starts losing its altitude. Mainly couple of reasons are responsible for stall. One reason is low airflow velocity. Slow airflow loses its energy due to friction on the wing and resulting flow separation. Another reason is when wing/aerofoil exceeds Angle of Attack (AoA) known as critical angle of attack. Airflow detaches from the wing surface and causes stall. In stall, wake of wing is produced.
To recover stall, first thing pilot do is, reduce the pitch angle of the aircraft which reduces AoA of the wing. Once AoA is reduced sufficiently pilot increases the engine thrust to increase aircraft speed.
Why is deep stall dangerous?
As explained above, stall produces wake of the wing. But most importantly the thing which makes deep stall dangerous is ineffectiveness of aircraft elevator located on the tail. In deep stall, wing is completely stalled & wake produced disturbs the flow over aircraft tail. Which makes elevator located on the tail of the aircraft ineffective. Elevator controls the pitching moment of the aircraft. Due to ineffectiveness of the elevator, pilot cannot reduce the aircraft pitch angle of aircraft and it becomes difficult to recover from deep stall.
Here comes The Aircraft Nerds Deep Stall Recovery System!
This is simply designed system which can be installed on the aircraft without making much modification in the aircraft. System consists of MEMs pressure sensors for the detection of the stall. At the instant when aircraft wing enters stall, pressure disturbances will be detected by these sensors. These signals will be sent to the microcontroller.
Aircraft are installed with various panels for maintenance purpose. Few such panel are also located just behind the elevator. These panels can be replaced with customized panels. This customized panel will consist of small centrifugal fans. These small fans will be activated, once pressure disturbance is detected by the pressure sensors. Fan rotation speed can be controlled by microcontroller. This will create forced airflow over elevator. It will make ineffective elevator effective again. Now the pilot can pitch down the aircraft and recover aircraft from the stall.
MEMs pressure sensors on the wing are small in size. They won't affect airflow much. Horizontal tail will have small air duct for creation of the forced flow. These ducts will also restrict the spanwise flow over the horizontal tail. and hence reducing induced drag.
By pressure sensors and customized panels deep stall can be recovered.