sacrificed. This is brought about by the need to overhaul the entire aircraft prior to 12,000 hours and at the same time, phase selected portions of it into various blocks/patterns.
EXAMPLE The buyer, desiring to establish a four block/pattern system, separates his maintenance program into four equal parts and places the items so separated into either block/pattern A, B, C, or D. Assuming the selection has been made, the blocks/patterns would look like this:
Block/pattern A = 4,000 hours (cumulative time = 4,000 hours) Block/pattern B = 4,000 hours (cumulative time = 8,000 hours) Block/pattern C = 4,000 hours (cumulative time = 12,000 hours) Block/pattern D = 4,000 hours (cumulative time = 16,000 hours) The effect on items in each block/pattern as the result of phasing them into a four block/pattern system would be as follows:
BLOCK/PATTERN A These items would have to be overhauled at 4,000 hours TSO for the buyer.
This would result in a loss of 8,000 hours "time remaining to overhaul."
BLOCK/PATTERN B These items would have to be overhauled at 8,000 hours TSO for the buyer.
This would result in a loss of 4,000 hours "time remaining to overhaul."
BLOCK/PATTERN C These items will be overhauled at 12,000 hours TSO for the buyer.
Since it was previously established through proration that this was the buyer's "time remaining to overhaul," no time will be sacrificed on the items scheduled in this block/pattern.
BLOCK/PATTERN D The items in this block/pattern will have to be overhauled at a point at, or prior to 12,000 hours and again at 16,000 hours in
order to properly phase them into the system. The initial time of overhaul of these particular items should be at the option of the buyer, providing they do not exceed 12,000 hours. There are several methods he may choose from to accomplish this initial overhaul. Among these are:
1. Initially O.H. all block/pattern D items in block/pattern A
2. Initially O.H. all block/pattern D items in block/pattern B
3. Initially O.H. all block/pattern D items in block/pattern C
4. Initially O.H. 1/2 of all block/pattern D items in block/pattern A and O.H. 1/2 of all block/pattern D items in block/pattern B
5. Initially O.H. 1/2 of all block/pattern D items in block/pattern B and O.H. 1/2 of all block/pattern D items in block/pattern C
6. Initially O.H. 1/2 of all block/pattern D items in block/pattern A and O.H. 1/2 of all block/pattern D items in block/pattern C
7. Initially O.H. 1/3 of all block/pattern D items in block/pattern A and O.H. 1/3 of all block/pattern D items in block/pattern B and O.H. 1/3 of all block/pattern D items in block/pattern C Because of the previously established prorated figure of 12,000 hours remaining to overhaul, the buyer stands to lose the same total amount of time regardless of which method he chooses.
Method #7 appears to be the most practical approach, since it would tend to spread the workload over a 12,000 hour period. The entire block/pattern D would, of necessity, have to be overhauled again at 16,000 hours at which time all items would be correctly phased into their proper block/pattern. Consideration should be given by the assigned inspectors to the extent of inspection (overhaul) required in the case of initial overhauls that are accomplished early solely for the purpose of phasing an aircraft into a block/pattern system.
In the foregoing example, it can readily be seen that block A items at the time of initial overhaul by the buyer will actually have accumulated only 7,000 hours since previously overhauled while block/pattern C items will have accumulated 15,000 hours.
In either case, it must be remembered that another 16,000 hours will pass before they are overhauled again.
---------------------------------------------------------------- ----------------------------------------------------------------
FIGURE 4. TRANSFER OF AIRCRAFT FROM A ONE-TIME OVERHAUL TO A
BLOCK/PATTERN SYSTEM (BUYER'S APPROVED OVERHAUL TIME LIMIT IS LOWER THAN THAT OF THE PREVIOUS OPERATOR.)
In this process it is first necessary to find the buyer's prorated "time since overhaul" and prorated "time remaining to overhaul" for the entire aircraft. This is accomplished by first applying the routine proration formula as shown below:
KNOWN 12,000 hours --- Previous operator's approved overhaul time limit.
3,000 hours --- Previous operator's time since overhaul.
8,000 hours --- Buyer's approved overhaul time limit which is to be divided into four blocks/patterns of 2,000 hours each (A, B, C, and D).
STEP I _____.250 --- Percent overhaul time used by 12,000/3,000.000 previous operator.
STEP II 8,000 --- Buyer's approved overhaul time limit.
x.250 -----
400.000 1,600.0 --------- 2,000.000 --- Buyer's prorated TSO.
STEP III 8,000 --- Buyer's approved overhaul time limit.
-2,000 --- Buyer's prorated TSO.
------ 6,000 --- Buyer's prorated time remaining to overhaul.
In this particular example, since the buyer has elected to transfer an aircraft from a one-time overhaul to a four block/pattern system, he should recognize that a substantial amount of his time remaining to overhaul will have to be sacrificed. This is brought about by the need to overhaul the entire aircraft prior to the accumulation of 6,000 additional hours and at the same time, phase selected portions of it into various blocks/patterns.
EXAMPLE The buyer, desiring to establish a four block/pattern system, separates his maintenance program into four equal parts and places the item so separated into either block/pattern A, B, C, or D. Assuming the selection has been made, the block/pattern would look like this:
Block/pattern A = 2,000 hours (cumulative time = 2,000 hours) Block/pattern B = 2,000 hours (cumulative time = 4,000 hours) Block/pattern C = 2,000 hours (cumulative time = 6,000 hours) Block/pattern D = 2,000 hours (cumulative time = 8,000 hours) The effect of items in each block/pattern as the result of phasing them into a four block/pattern system would be as follows:
BLOCK/PATTERN A These items would have to be overhauled at 2,000 hours TSO for the buyer.
This would result in a loss of 4,000 hours "time remaining to overhaul."
BLOCK/PATTERN B These items would have to be overhauled at 4,000 hours TSO for the buyer.
This would result in a loss of 2,000 hours "time remaining to overhaul."
BLOCK/PATTERN C These items will be overhauled at 6,000 hours TSO for the buyer.
Since it was previously established through proration that this was the buyer's "time remaining to overhaul," no time will be sacrificed on the items scheduled in this block/pattern.
BLOCK/PATTERN D The items in this block/pattern will have to be overhauled at a point at, or prior to 6,000 hours and again at 8,000 hours in order to properly phase them into the system. The initial time of overhaul of these particular items should be at the option of the buyer, providing they do not exceed 6,000 hours. There are several methods he may choose from to accomplish this initial
overhaul. Among these are:
1. Initially O.H. all block/pattern D items in block/pattern A
2. Initially O.H. all block/pattern D items in block/pattern B
3. Initially O.H. all block/pattern D items in block/pattern C
4. Initially O.H. 1/2 of all block/pattern D items in block/pattern and O.H. 1/2 of all block/pattern D items A in block/pattern B
5. Initially O.H. 1/2 of all block/pattern D items in block/pattern and O.H. 1/2 of all block/pattern D items B in block/pattern C
6. Initially O.H. 1/2 of all block/pattern D items in block/pattern and O.H. 1/2 of all block/pattern D items A in block/pattern C
7. Initially O.H. 1/3 of all block/pattern D items in block/pattern and O.H. 1/3 of all block/pattern D items A in block/pattern and O.H. 1/3 of all block/pattern D items B in block/pattern C Because of the previously established prorated figure of 6,000 hours remaining to overhaul, the buyer stands to lose the same total amount of time regardless of which method he chooses.
Method #7 appears to be the most practical approach, since it would tend to spread the workload over a 6,000 hour period. The entire block/pattern D would, of necessity, have to be overhauled again at 8,000 hours at which time all items would be correctly phased into their proper block/pattern. Consideration should be given by the assigned inspectors to the extent of inspection (overhaul) required in the case of initial overhauls that are accomplished early solely for the purpose of phasing an aircraft into a block/pattern system.
In the foregoing example, it can readily be seen that block A items at the time of initial overhaul by the buyer will actually have accumulated only 5,000 hours since previously overhauled while block/pattern C items will have accumulated 9,000 hours.
In either case it must be remembered that another 8,000 hours will pass before they are overhauled again.
---------------------------------------------------------------- ---------------------------------------------------------------- FIGURE 5. FORMAT FOR PRESENTATION OF PRORATION
DATA ON AIRCRAFT BEING TRANSFERRED Previous Operator (__________) Buyer (_________) Identify Identify
Block/Pattern Approved Time Percent of Approved Pro- Proor Component Overhaul Since Overhaul Overhaul rated rated & Serial No. Time Over- Time Used Time T.S.O. Time haul To Overhaul (16000) Respective (12000) Respective Block/ Block/ Pattern Pattern Block/Pattern A 4000 3000 .187 12000 2244 9756 Block/Pattern B 4000 15000 .937 12000 11244 756 Block/Pattern C 4000 11000 .687 12000 8244 3756 Block/Pattern D 4000 7000 .437 12000 5244 6756 ---------------------------------------------------------------- ---------------------------------------------------------------- FIGURE 6. TRANSFER OF PREVIOUSLY PRORATED AIRCRAFT An aircraft was acquired by operator "X" and placed on his maintenance program through the proration process. After acquisition, "X" operated the aircraft for an additional 1,000 hours.
1. 12,000 hours = approved overhaul time for "X".
2. 3,000 hours = prorated TSO for "X" at time of acquisition.
3. 2,000 hours = actual TSO at time of acquisition by "X".
4. 1,000 hours = additional flight time added to aircraft by "X".
5. 3,000 + 1,000 = 4,000 hours - "X's" prorated TSO.
6. 2,000 + 1,000 = 3,000 hours - actual TSO on aircraft.
Operator "X" now desires to transfer the aircraft to operator "Y". The overhaul time is to be prorated for operator "Y" and his approved overhaul time is 14,000 hours.
7. 3,000 divided by 12,000 = .250 of overhaul time used by "X".
8. 14,000 hours = approved O.H. time for "Y".
9. 14,000 x .250 = 3,500 hours prorated TSO for "Y".
10. 14,000 - 3,500 = 10,500 hours remaining to overhaul for operator "Y" at time of transfer.
NOTE: Actual TSO (Step 7) was used for purpose of proration to operator "Y", not the prorated TSO.
* The buyer of a previously prorated aircraft whose approved overhaul time limits are identical to the previous operators may utilize the remaining prorated time of the previous operator.
When a buyer uses the remaining prorated time, a document shall be prepared listing the previous operator or operators' approved overhaul times on which the proration was based and shall be made part of the operations specifications by means of a preface page such as the example shown in Appendix 1, Figure 12. * ---------------------------------------------------------------- ---------------------------------------------------------------- FIGURE 7. PROCEDURES FOR CONVERTING CALENDAR OVERHAUL (MONTHS) TO HOURS SINCE OVERHAUL FOR PRORATION
PURPOSES
METHOD A Previous operator's overhaul time limit is 18 months: (360 + 180 = 540.
Previous operator's time since overhaul is 180 days.
Buyer's approved overhaul time limit is 2,000 hours.
COMPUTATIONS 180 --- = .333 time since overhaul.
540 .33 of 2,000 hours = 666 hours prorated time since overhaul for buyer.
2,000 hours - 666 = 1,334 hours. Buyer's prorated time remaining to overhaul.
METHOD B Previous operator's overhaul time limit: 18 months or 540 days.
Previous operator's utilization time: 8 hours per day.
Previous operator's overhaul time limit in hours: (540 days x 8 hrs.) = 4,320.
Previous operator's time since overhaul (180 x 8 hours) = 1,440 hours.
Buyer's overhaul time limit is 2,000 hours.
COMPUTATIONS 1400 Time since overhaul in percent: ---- = .333 4320 .333 of 2,000 hours = 666 hours prorated time since overhaul.
2,000 hours - 666 = 1,334 hours. Buyer's prorated time remaining to overhaul.
---------------------------------------------------------------- ---------------------------------------------------------------- FIGURE 8. METHOD OF DEPICTING AREAS, SECTIONS, COMPONENTS, ETC.,
THAT ARE TIED TO A SPECIFIC BLOCK The following presentation is an example of how items such as areas, sections, and appliances are included in a block.
An operator should submit such items and relate the items to the block, or submit actual time for each item.
Block/Pattern Block/Pattern Block/Pattern Block/Pattern
A B C D Nose gear Center Section Right wing fuel Empennage assembly & cells components Steering Left wing fuel Lights Ruddermechanism & cells vertical fin controls Accumulators Pylons, Nos. Electrical Stabilizer 1 & 2 units, components, connections, Nose gear doors Lines etc.
Brackets, Electrical Hydraulics Tail hinges, etc. connections Compartment Lights, wires, Flaps Lights etc.
Air inlets & Spoilers Booster anti-icing control Hydraulic
fittings Main landing gear assembly ---------------------------------------------------------------- ---------------------------------------------------------------- FIGURE 9. OPERATIONS SPECIFICATIONS - PREFACE PAGE
FOR AIRCRAFT ON PRORATED TIME Form Approved.
UNITED STATES OF AMERICA Budget Bureau FEDERAL AVIATION AGENCY No. 04-R075.
WASHINGTON Page of Page
OPERATIONS SPECIFICATIONS
AIRCRAFT MAINTENANCE - GENERAL
PREFACE PAGE FOR AIRCRAFT ON PRORATED TIME The aircraft listed herein, including powerplants, propellers, and appliances which have prorated times, shall be overhauled in accordance with their respective limitations as set forth in:
Operations Specifications Aircraft Maintenance Amendment No. _____, Dated _____ These specifications are applicable to: Aircraft N_____ - Serial No. ____, its powerplants, propellers, and appliances until they are first overhauled. Thereafter, these specifications are cancelled and the aircraft will be inspected and overhauled in accordance with the _____ airlines maintenance program and the approved time limits.
Records maintained on the above aircraft shall show the actual and adjusted time since overhaul and, thereafter, such time in service shall be added thereto.
Effective date _____________________ ---------------------------------------------------------------- ----------------------------------------------------------------
FIGURE 10. OPERATIONS SPECIFICATIONS AIRCRAFT
MAINTENANCE - GENERAL Form Approved.
UNITED STATES OF AMERICA Budget Bureau FEDERAL AVIATION AGENCY No. 04-R075.
WASHINGTON Page of Page
OPERATIONS SPECIFICATIONS
AIRCRAFT MAINTENANCE - GENERAL (Part 121) Irrespective of the type of operation to be conducted by (name of operator), the continuous airworthiness and inspection program limitations which are described and specified in these Operations Specifications shall be applicable to all (name of operator) aircraft listed and authorized for use under Federal Aviation Regulations 121.
The operator shall provide in its currently effective Maintenance Manual a comprehensive maintenance program necessary to fulfill its responsibility to maintain the aircraft in an airworthy condition in accordance with applicable Federal Aviation Regulations and Standards prescribed and approved by the Administrator.
The aircraft and its component parts, accessories, and appliances shall be maintained in an airworthy condition in accordance with the maximum time limits hereinafter set forth for the accomplishment of the overhaul, periodic inspections, and routine checks of the aircraft and its component parts, accessories, and appliances.
"On Condition" items will be maintained in a continuous airworthy condition by periodic and progressive inspections, checks, services, repair, and/or preventive maintenance and shall be appropriately described in the operator's Maintenance Manual.
Effective date _____________________ ---------------------------------------------------------------- ---------------------------------------------------------------- FIGURE 11. OPERATIONS SPECIFICATIONS - PREFACE PAGE
FOR AIRCRAFT ON PRORATED TIME Form Approved.
UNITED STATES OF AMERICA Budget Bureau
FEDERAL AVIATION AGENCY No. 04-R075.
WASHINGTON Page of Page
OPERATIONS SPECIFICATIONS
AIRCRAFT MAINTENANCE - GENERAL
PREFACE PAGE FOR AIRCRAFT ON PRORATED TIME The aircraft listed hereon, including powerplants, propellers, and appliances which have prorated times, shall be overhauled in accordance with the respective limits as set forth in:
Proration Document No. __________ Dated ________ This document is applicable to: Aircraft N ____ - Serial No.
_____, its powerplants, propellers, and appliances until they are first overhauled. Thereafter, this document is cancelled and the aircraft will be inspected and overhauled in accordance with the _____ airlines maintenance program and the approved time limits.
Records maintained on the above aircraft shall show the actual and adjusted time since overhaul and, thereafter, such time in service shall be added thereto.
Effective date _____________________ ---------------------------------------------------------------- ---------------------------------------------------------------- * FIGURE 12. OPERATIONS SPECIFICATIONS - PREFACE PAGE FOR
AIRCRAFT USING PREVIOUS OPERATORS REMAINING PRORATED TIMES.
Form Approved.
UNITED STATES OF AMERICA OMB No. 04-R0075
DEPARTMENT OF TRANSPORTATION
FEDERAL AVIATION ADMINISTRATION
WASHINGTON
OPERATIONS SPECIFICATIONS
AIRCRAFT MAINTENANCE - GENERAL
PREFACE PAGE FOR AIRCRAFT ON PRORATED TIME The aircraft listed hereon had the airframe overhaul times prorated when it was transferred from _____ Airlines with an FAA approved overhaul time of 16,000 for the airframe to _____ Airlines with an approved time of 12,000 hours. The aircraft is now operated by _____ Aviation who also has 12,000 hours airframe overhaul time. Therefore this aircraft is approved to use the remaining prorated time of _____ Airlines and shall be overhauled in accordance with the respective limits set forth in:
Proration Document No. _______________________________ Dated _____________________________ This document is applicable to: Aircraft N __________ - Serial No. _____, until its first overhaul. Thereafter, this document is cancelled and the aircraft will be inspected and overhauled in accordance with the __________ airlines maintenance program and the approved time limits.
Records maintained on the above aircraft shall show the actual and adjusted time since overhaul and, thereafter, such time in service shall be added thereto.
Effective date _________________________ ---------------------------------------------------------------- Appendix 2 ---------------------------------------------------------------- FIGURE 1. OPERATIONS SPECIFICATIONS AIRCRAFT MAINTENANCE
- AVIONICS Form Approved.
UNITED STATES OF AMERICA Budget Bureau FEDERAL AVIATION AGENCY No. 04-R075.
WASHINGTON PART D PAGE 1 of 2 PAGES