Boeing 787 Ram Air Turbine

[MX Trainer]

I am looking for some in depth information on the RAT as installed on the 787.

Google has been a friend - but not a very technical one!!

I understand that it is used to power both hydraulic and electrical and am curious as to whether it has a speed control like many other RATs.

Any links to schematics and drawings would be appreciated.

In addition anything that is different about it than the 777 or 767 would be appreciated.

Thanks in advance.

Regards,

Mx

[MX Trainer]

Re - Constant Speed and Over-Speed Control of Sundstrand Ram Air Turbines

Thanks to DaveReidUK for the link to manufacturer.


Here is the link to the Sundstand patent for about 1988

Patent US4743163 - Ram air turbine control system - Google Patents (http://www.google.com/patents/US4743163)

- this has the speed governor that is referenced in the second patent info regarding the Over-Speed protection.

RAM air turbine over-speed protector using redundant yoke plate linear bearings - Hamilton Sundstrand Corporation (http://www.freepatentsonline.com/7074010.html)

Since I still do not have info regarding the 787 RAT I can not say for sure this will apply - but I would expect it to be the same or similar as a RAT is a RAT is a RAT.

This excerpt from the over-speed patent is probably the biggest reason for at least overspeed control.

BACKGROUND OF THE INVENTION

A ram air turbine (RAT) is a device for generating emergency supplemental power in a wide variety of aircraft. A RAT may generate hydraulic power, electric power or both. A RAT incorporates a turbine that extracts power from an air stream proximate the aircraft in flight. A typical RAT in current use is described in U.S. Pat. No. 4,743,163 to Markunas et al., owned by the assignee of this application, and incorporated herein by reference. The turbine is coupled to suitable power generating equipment, such as a hydraulic pump for hydraulic power and an electric generator for electric power.
As described in Markunas et al., the turbine includes a speed governor that changes the turbine blade position to maintain a relatively constant shaft speed to the power generating equipment. Failure of the turbine speed governor can cause an over-speed condition that may ultimately cause the release of a turbine blade at very high speed. Due to the high speed, the wayward blade has very high energy as well. The most common cause of governor failure is due to seizure of the bearing between the governor shaft and the governor yoke plate that controls the pitch of the turbine blades.
The potential release of a high energy blade proximate the aircraft is a concern for both commercial and military RAT applications. Should the wayward blade strike the aircraft fuselage, it may penetrate the skin and cause damage to electric or hydraulic power equipment or control systems. It may also injure passengers or crew. If one of the propulsion engines ingests the wayward blade, the engine may suffer severe damage that results in loss of thrust.
Current methods to minimise hazards caused by turbine over-speed-induced release of a turbine blade have involved strategic placement of key elements or shields to prevent penetration. These methods no longer satisfy increasingly stringent certification and safety requirements promoted by airworthiness authorities.



Regards,

Mx

[MX Trainer]

Bump

1000+ looks and nobody has any info????

Must be some pretty secret stuff!!! LOL

Mx

[TURIN]

From memory (its a while since I did the course) the RAT gen is frequency wild. The a/c electronics sort the frequency/voltage out.
It is a hybrid RAT, so yes it supplies hydraulics too. Not sure about constant speeding though. Variable pitch, yes, to maximise efficiency.


Posted from Pprune.org App for Android

[MX Trainer]

Information on the B787 Ram Air Turbine:


I have 3 different sources of information relating to the speed control of the RAT on the 787 - all 3 confirm that the blades change pitch as a function of the speed limiter - which at the higher aircraft airspeeds or the offloading of the RAT will maintain a maximum constant speed of the turbine.

Quick link to the manufacturers site with just a quick overview of their product line;

Aircraft Ram Air Turbine (RAT) | UTC Aerospace Systems (http://utcaerospacesystems.com/cap/products/Pages/ram-air-turbine-systems.aspx)

Thanks to all of you for your information - it is appreciated:D

Regards,

Mx