IV Grammar. Scan the text to fill in the gaps with correct prepositions.

1 …… certain emergency conditions the typical aircraft power generation system may not meet all the airworthiness authority requirements and additional sources … power generation may need to be used …. power the aircraft systems.

2 The aircraft battery offers a short-term power storage capability, typically … … 30 minutes.

3 However … longer periods … operation the battery is insufficient.

4 The operation … twin- engined passenger aircraft … ETOPS flights now means

that the aircraft has to be able to operate … one engine while … to 180 minutes

… an alternative or diversion airfield.

5 This has led … modification … some … the primary aircraft systems, including

the electrical system, … ensure that sufficient integrity remains … accomplish

the 180 minute diversion while still operating … acceptable safety margins.

6 There are three standard methods … providing back-… power … civil transport

aircraft.

7 The RAT is an air driven turbine, normally stowed … the aircraft ventral or nose

section that is extended either automatically or manually when the emergency

commences.

8 The passage of air … the turbine is used … power a small emergency generator

… limited capacity, usually enough … power the crew’s essential flight

instruments and a few other critical services.

9 Typical RAT generator sizing may vary …. 5 to 15 kVA depending … the

aircraft.

10 The RAT also powers a small hydraulic power generator … similar hydraulic

system emergency power provision.

11 Once deployed then the RAT remains extended … the duration … the flight and

cannot be restored …. maintenance action … the ground.

12 The RAT is intended … furnish the crew … sufficient power fly the aircraft

while attempting … restore the primary generators or carry …. a diversion …

the nearest airfield.

13 It is not intended … provide significant amounts … power … a lengthy period

… operation.