The surface is forced to land a floating system, and when it encounters a forced landing, it is assumed that this system can improve the flight crew to escape the helicopter.
The original design of the US Navy's SH-60B includes a surface emergency landing floating system. The system is mounted on the short wing above the main landing gear on either side of the aircraft, just behind the cockpit. The floating medium is helium and is released into the bladder via an explosive pack starter or valve. The position of the floating bladder is considered to be the most effective and stable for SH-60B.
When the design of the SH-60F is carried out, its operating experience and tests show the shortcomings of this system, especially related to the SH-60F design. The disadvantages of this system are:
- The shape and position of the airbag poses a risk of escape for the pilot
- There is no helium required to fill the airbag on the naval ship
- Nitrogen replacement of helium increases airbag filling time
- No safety failure mechanism
- The fuselage does not meet the strength required to fly forward and enter the water surface
The above problem (1) has the greatest potential for flight crew members and problem solving. Once the airbag is inflated, the cockpit doors and windows are partially obstructed even if they are still in the water. The cockpit door can't be opened at all, and the window is difficult to discard in the best case. When the airbag partially blocks the window, even after the glass is discarded, it is still difficult for the flight crew to escape because it is necessary to wear the survival equipment. If the helicopter floats in a vertical tail down position, the risk of escape will increase. The solution to this problem is to modify the shape of the floating bladder or move to the transition section. However, relevant data show that the survival rate is close to 70% with or without a helicopter floating system.
The solution to the above problem (2) is to modify the system to use nitrogen. Available in ready-to-use nitrogen on US Navy ships, including SH-60 landing gear and rotor dampers. However, nitrogen does not provide the same buoyancy as helium, so the floating system is not as effective as the original design. The SH-60F, SH-60B and HH-60H helicopters were switched to nitrogen.
The above problem (3) arises due to the suggested solution to the problem (2). When nitrogen was used, the average inflation time was increased to 72 seconds. According to the demand, the maximum inflation time is 8 seconds. The electronically actuated valve replaces the explosive pack starter during the test to reduce the average inflation time to 6 seconds. The SH-60F, SH-60B and HH-60H helicopters were replaced with electronically actuated valves.
The modification of the above problem (4) is to add 1 to the filling line of the 2 pipe system between the valve and the air bag. If one valve cannot be opened, this will ensure that 2 airbags are filled. The SH-60F, SH-60B and HH-60H helicopters use this modification. Another suggestion is to add a brine or hydrostatic actuation system to supplement the manual switch, which is the only actuation method for the SH-60B floating system. This modification was not performed.
To solve the above problem (5), the US Navy recommends that manufacturers improve the strength of the contact points, and when the airbag is inflated, it can withstand a forward rate of 30,000 tons and a sinking rate of 6 inches per second. When the airbag is inflated, the contact point can also withstand a forward rate of 20,000 tons without causing a flight safety event. The evidence indicates that no modifications have been implemented.
Due to the history of the SH-60B/F and HH-60H floating systems, engine reliability improvements and MH-60R/S project upgrades, the floating system is not installed in the MH-60R and MH-60S. The integration of floating systems raises some safety risks, including the blocking of flight crews' emergency escape routes. Because of these risks, the MH-60R has never been designed to contain a floating system. The MH-60R is followed by the development of the MH-60S, and the floating system is not considered. The survival rate of the shipwreck was basically the same before and after the system was removed. Finally, the SH-60B/F floating system installation location is now the location of the MH-60R and MH-60S active vibration control system power generators.