CVN 72 - Abe Lincoln

Richard Cobb
January 1992

These photos were taken while working for NKF Engineering in 1992. I was on the Aircraft Carrier 'Abe Lincoln' (CVN-72) for 6 days while at sea off the California coast. Air operations were conducted around the clock during that time - mainly as qualification/re-qualification for pilots needing to obtain a carrier landing rating, or to keep it current.

I was on the ship to collect vibration data from the 'arresting engines', which stop the aircraft on landing. Think of a 30 foot long hydraulic cylinder (similar to a very large automobile lift in a service station) that is oriented horizontally with multiple pulley sheaves on each end (see images 74-83 below). A large steel cable passes through the sheaves and runs to the carrier deck. The hydraulic cylinder begins at a fully extended position. After an aircraft snags a landing cable, the cable compresses the hydraulic cylinder (making it shorter in length). The hydraulic fluid in the cylinder passes through a controlled orifice which decreases in size as the cylinder compresses. This also has an additional setting for the size of the aircraft, with smaller orifices for larger weights. There are 5 or 6 cables on deck that an aircraft may hook on to. Each of these has two arresting gear engines connected to it.

A problem had arisen on one carrier that had sheave bearings installed that were not properly heat treated, and they had failed prematurely. The question was whether other carriers also had these defective bearings. Considerable time and effort (estimated $50k in 1992 dollars) was required to disassemble and replace the bearings in an engine. 'Condition Monitoring' uses vibration data to determine if there are 'pits' in bearing races, which are an indicator of impending failure. By noting the rotational speed and comparing intermittent vibration spikes to the speed, it is possible to identify pits because they generate a brief vibration pulse every time a ball/roller encounters one. My instrumentation consisted of an optical sensor and a mark on the side of a pulley (image 80 shows a close-up), and accelerometers mounted inside of the pulley shaft (see #83). During my week onboard I collected data from multiple engines. (Later processing showed no significant signs of deterioration, so the bearings were not changed until the next normal overhaul period, thus saving considerable expense).

During this period a couple of crew members I had become acquainted with took me on deck while operations were on-going. I was on deck next to the arresting cables as aircraft landed (pics 33-41), and between the catapults as they took off (62-66). It was one of those lifetime memorable experiences!

Some interesting points:

Even though I have served in the military, I was still impressed by the precision of operations onboard an aircraft carrier. It requires 100's of people working simultaneously to conduct air operations. Planes land, are unhooked and moved in quick succession on one part of the deck, while only a few yards away planes are also taking off. Any one person failing to do their job properly could result in major difficulties or disaster. Yet, after a few days it all seems to be 'routine'.

My final thrill for this trip was to be catapulted off the carrier on a COD (Carrier Onboard Delivery) flight. These are propellor aircraft which haul mail, personnel, etc, similar to #23. With no windows there was nothing to see, but it was still quite a thrill. All passengers are strapped in with full harnesses and given instructions for body position during takeoff. The g-force was quite impressive, but it was over in an instant.

CVN72_01 CVN72_02 CVN72_03 CVN72_04 CVN72_05
CVN72_01 CVN72_02 CVN72_03 CVN72_04 CVN72_05
CVN72_06 CVN72_07 CVN72_08 CVN72_09 CVN72_10
CVN72_06 CVN72_07 CVN72_08 CVN72_09 CVN72_10
CVN72_11 CVN72_12 CVN72_13 CVN72_14 CVN72_15
CVN72_11 CVN72_12 CVN72_13 CVN72_14 CVN72_15
CVN72_16 CVN72_17 CVN72_18 CVN72_19 CVN72_20
CVN72_16 CVN72_17 CVN72_18 CVN72_19 CVN72_20
CVN72_21 CVN72_22 CVN72_23 CVN72_24 CVN72_25
CVN72_21 CVN72_22 CVN72_23 CVN72_24 CVN72_25
CVN72_26 CVN72_27 CVN72_28 CVN72_29 CVN72_30
CVN72_26 CVN72_27 CVN72_28 CVN72_29 CVN72_30
CVN72_31 CVN72_32 CVN72_33B CVN72_34 CVN72_35
CVN72_31 CVN72_32 CVN72_33B CVN72_34 CVN72_35
CVN72_36 CVN72_37 CVN72_38 CVN72_39 CVN72_40
CVN72_36 CVN72_37 CVN72_38 CVN72_39 CVN72_40
CVN72_41 CVN72_42 CVN72_43 CVN72_44 CVN72_45
CVN72_41 CVN72_42 CVN72_43 CVN72_44 CVN72_45
CVN72_46 CVN72_47 CVN72_48 CVN72_49 CVN72_50
CVN72_46 CVN72_47 CVN72_48 CVN72_49 CVN72_50
CVN72_51 CVN72_52 CVN72_53 CVN72_54 CVN72_55
CVN72_51 CVN72_52 CVN72_53 CVN72_54 CVN72_55
CVN72_56 CVN72_57 CVN72_58 CVN72_59 CVN72_60
CVN72_56 CVN72_57 CVN72_58 CVN72_59 CVN72_60
CVN72_61 CVN72_62 CVN72_63 CVN72_64 CVN72_65
CVN72_61 CVN72_62 CVN72_63 CVN72_64 CVN72_65
CVN72_66 CVN72_67 CVN72_68 CVN72_69 CVN72_70
CVN72_66 CVN72_67 CVN72_68 CVN72_69 CVN72_70
CVN72_71 CVN72_72 CVN72_73 CVN72_74 CVN72_75
CVN72_71 CVN72_72 CVN72_73 CVN72_74 CVN72_75
CVN72_76 CVN72_77 CVN72_78 CVN72_79 CVN72_80
CVN72_76 CVN72_77 CVN72_78 CVN72_79 CVN72_80
CVN72_81 CVN72_82 CVN72_83
CVN72_81 CVN72_82 CVN72_83

(updated August 15, 2012)

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