787 deployed RAM Air Turbine

[tflash]

I wonder why so many of these 787's land with their Ram Air Turbine deployed?

 

Problems with battery power ? See eg 00:42 onwards.

 

[SilentGun]

:huh: That's strange... seems like it would get damaged over time during landings.

 

Good catch! that's definitely something to look into.

[Stickers]

Well there are a lot of reasons the RAT can be deployed. Could be MX requested it to be deployed for inspection, which provides training for stowing it also.

[Cp]

Came across this whilst googling:

787 NO-BLEED SYSTEMS

The key difference between the traditional and 787 hydraulic system is the power source for the center system. In the traditional architecture, the center system is powered by two large air-turbine-driven hydraulic pumps, which operate at approximately 50 gallons per minute (gpm) at 3,000 pounds per square inch (psi) to meet peak hydraulic demands for landing gear actuation, high lift actuation and primary flight control during takeoff and landing. During the remainder of the flight, two small (approximately 6 gpm) electric-driven hydraulic pumps power the center system.

Seems like that turbine drives two hydraulic pumps directly and not an electric generator.

[IvanK]

Be interesting to see if this is a Date based thing. i.e. a Temporary procedure mandated by the manufacturer as a risk mitigation thing .... like an Airbus OEB type thing ?

 

i.e. those with RAT deployed are affected aircraft or the video of those with RAT's deployed was taken during the effectivity of the procedure ?

[Snarf]

Traditionally hydraulic systems are powered by engine driven pumps (EDPs) supplemented with electrical pumps. The mention of air driven hydraulic pumps bemuses me as I know of no aircraft which does this. The 787 though is almost wholly electric in its power for systems which were traditionally powered by customer air, this includes the air conditioning and pressurisation systems which consume a lot of air. On the 787 these are now driven by electric motors.

 

My guess with regard to RAT employment is that the engines are at idle minimising electrical power and they are supplementing that with the RAT power out put.

[Andrei]

My guess with regard to RAT employment is that the engines are at idle minimising electrical power and they are supplementing that with the RAT power out put.

 

I share your view. Also it might be done for extra redundancy in case you would get an engine or both engines out during the approach. Might be part of airline SOP or something actually recommended by Boeing until they get decent operating statistics.

[Druid_]

^ correct. The hyd pumps on the 787 are driven electrically. The only bleed system on the 787 is for engine anti-ice.

 

You would only deploy the RAT as part of a checklist or the aircraft might deploy it automatically if a certain failure or combination of failures occurred.

 

If I had to guess I would say it was deployed to supplement electrical power due to failure of a large electrical power source like say an engine generator or a battery/capacitor problem.

[IvanK]

are all the RAT deployed 787's -900 variants ?

 

"Last year, Boeing received a waiver from the FAA that allowed it to deliver its first 787-9, a stretched version of the Dreamliner, even after two components failed to meet airworthiness regulations.One of those components was linked with the ram air turbine and needed to be redesigned to improve its reliability after it failed a noncertification flight test. The redesign was not ready until early 2015, more than six months after the first 787-9 entered service in mid-2014.

When Boeing sought the exemption, it argued that the chances of a dual engine failure and total loss of power were extremely remote."

 

 

From here:

http://www.theage.com.au/it-pro/business-it/boeing-warns-all-787s-should-be-turned-off-and-on-again-to-avoid-potential-crash-20150503-1mz51i.html

[TIMBER SOUR]

I didn't read the description, but if the video was filmed at BFI, then its probably pre-dlivery test flights being flown, and there's a checklist of things to accomplish on each airplane before customer acceptance. RAT/ADG deployment is likely on the checklist, hence the video.

[wingnut]

Timber Sour is correct.

 

This video is done at the Boeing manufacture plant near Seattle. Part of the certification of every aircraft is a flight verifying the operation of the RAT.

 

The only time you should see the RAT deployed on a commercial flight is in an emergency electrical configuration (batts only) or depending on the aircraft (B787) low hydraulic pressure on all three systems.

[tflash]

That would be a good explanation indeed!