RAM’s Trade-A-Plane publication has been superseded by RAM’s
Comment published to the NPRM docket at: FAA-2012-0002-0571,
which can also be viewed on RAM’s website at:
http://www.ramaircraft.com/NPRM/cl09_RAM_Comments_to_NPRM_Docket.pdf
To all our friends and customers in General Aviation:
In the First September 2013 issue of Trade-A-Plane, RAM Aircraft published our Initial Viewpoint
on the Recent Cylinder Notification of Proposed Rule Making (NPRM), and we encouraged each of you to help the FAA by responding to their request for Comments. At that time we were gathering the facts and attempting to understand the situation. After gathering those facts we offer the following:
Page 63 of the FAA’s Airworthiness Directives Manual (8040.1C) requires that the NPRM must include FAA reports, summaries or lists of facts, or data that
support the AD action. The NPRM does not contain the required information. The FAA’s Safety Risk Management Policy (Order 8040.4A) establishes the
processes the FAA uses to decide whether to issue an AD. Appendix C of 8040.4A provides the Safety Risk Definition Tables and Risk Matrix (see below) that
are used to determine the acceptability of a safety risk. The Risk Matrix requires having enough information to determine both: (a) the likelihood of a cylinder
separation; and (b) the severity of a cylinder separation. The NPRM lacks enough information to determine either the likelihood or the severity of a cylinder separation. So, RAM researched its own data and ran engine tests to determine both the likelihood and the severity of a cylinder separation. Here is what we learned:
LIKELIHOOD OF A SEPARATION- Fact: The Likelihood of a Separation is "Extremely Improbable"
Cyl Hrs per Eng Hrs per A/C Flt Hrs per Avg Flt
A/C Type Cyl Sold Cyl Flt Hrs Eng Flt Hrs Tot Sep'd Separation Separation
Separation
Hrs/Yr
Twin
11,632 9,072,681 1,512,113
22
412,395
68,732
34,366
128.5
Single
1,982 1,095,110
182,518
3
365,037
60,839
60,839
94.2
A/C Flt Yrs per
Separation
267
646
RAM sold to its target market of big-bore, Continental engines, a total of 13,614 cylinders affected by the NPRM. RAM reported 25 cylinders to the FAA.
Together with the 29 cylinders published in the NPRM Docket, and eliminating duplicate reports, RAM now knows of 48 cylinder failures reported to the FAA.
The calculations presented herein use only RAM’s data because we know our data is accurate. We used the FAA’s GA Activity Surveys, found at:
http://www.faa.gov/data_research/aviation_data_statistics/general_aviation/ to find the average number of flight hours for single and multi-engine aircraft
between 2002 and 2013. RAM sold 85% of its cylinders to multi-engine, and 15% to single-engine aircraft. Those 13,614 cylinders have flown a calculated
1,694,631 engine hours. That’s one cylinder separation for every: (a) 34,366 multi-engine aircraft flight hours, or 267 average years of operation for a multi-engine
aircraft; and (b) 60,839 single-engine aircraft flight hours, or 646 average years of operation for a single-engine aircraft. Clearly the “Likelihood of a Separation”
must be plotted in the Risk Matrix in row E, “Extremely Improbable,” which is defined as “so unlikely that it is not expected to occur, but it is not impossible.”
SEVERITY OF A SEPARATION: Testing Proved with 1 or 2 Separated Cylinders the Severity is "Minimal"
Test Cum.
Time
Cell
Fuel
Oil
Oil
Time Temp M P RPM Flow Torque H P % H P Press Temp
39.0 2695 31.5
31.9 2405 21.0
1
2
EGT (F°)
3
4
5
6
1
2
CHT (F°)
3
4
5
6
Baseline Run: RAM 335 HP CMI TSIO-520-NB; S/N 509811
664 341 102% 62
186 1473 1445 1442 1449 1436 1404 382 359 342 361 379 386
556 254 76%
60
187 1477 1462 1451 1462 1455 1422 392 367 352 371 382 394
7:16
12:19
93
92
15:54 15:54
40:03 40:03
Test Run #1: RAM 335 HP CMI TSIO-520-NB; S/N 509811; With One Cyl Head-Barrel Separation; #6 S/N 48916-18
105 39.5 2692 38.4
539 276 82%
64
174 1472 1434 1445 1425 1442 403 375 357 345 352 388 133
110 37.6 2438 28.5
542 252 75%
59
186 1471 1424 1453 1407 1443 240 405 374 376 367 410 128
Test Run #2: RAM 335 HP CMI TSIO-520-NB; S/N 509811; With Two Cyl Head-Barrel Separations; #5 S/N 51847-12; #6 S/N 48916-18
7:58 48:01
91 39.1 2705 34.1
413 213 63%
67
161 1454 1460 1453 1450 341 430 381 366 369 353 110 119
48:27 88:30
94 38.0 2544 29.5
415 201 60%
62
177 1476 1474 1453 1449 254 402 401 385 377 369 107 126
ECi provided RAM with 2 cylinders that had head-barrel separations. On September 11th and 12th, 2013 we performed 2 test cell runs. Test Run #1 with 1 separated
cylinder produced 80%+ power and easily made 75% power, a normal cruise power setting per Cessna’s Pilot’s Operating Handbooks. After 40 minutes we shut
the engine down in order to install the second separated cylinder. Test Run #2 with 2 separated cylinders produced 63% power and easily made 60% power, also
a normal cruise power setting per Cessna’s Pilot’s Operating Handbooks. We concluded the tests with a normal shutdown after running an additional 48 minutes.
Remember, Cessna publishes performance charts for its aircraft using 50% cruise power and even less. RAM’s test runs prove that even with 2 separated cylinders
there is only a “negligible safety effect,” which on the Risk Matrix plots the “Severity” in column 5.
Table C-1: Severity Definitions
Excerpted from FAA Document 8040.4A (Safety Risk Management Policy), Appendix C.
Severity
Likelihood
Minimal
5
Minor
4
Major
3
Hazardous Catastrophic
2
1
Frequent
A
Probable
B
Minimal - 5
Negligible Safety Effect
Minor - 4
- Physical discomfort to persons
-Slight damage to aircraft/vehicle
Major - 3
- Physical distress or injuries to
persons
- Slight damage to aircraft/vehicle
Hazardous - 2
Multiple serious injuries; fatal injury
to a relatively small number of
persons (one or two); or a hull loss
without fatalities
Catastrophic - 1
Multiple fatalities (or fatality to all on
board) usually with the loss of
aircraft/vehicle
Remote
C
Extremely
Remote
D
Table C-2: Likelihood Definitions
Extremely
Improbable
E
*
Figure C-1: Risk Matrix
Unacceptable Risk
Acceptabe Risk with Mitigation
Acceptable Risk
*
Unacceptable with Single
Point and/or Common
Cause Failures
Frequent - A
Expected to occur routinely
Probable - B
Expected to occur often
Remote - C
Expected to occur infrequently
Extremely Remote - D
Expected to occur rarely
Extremely Improbable - E
So unlikely that it is not expected to
occur, but it is not impossible
RESULT: Proposed AD Should Be Withdrawn
When RAM’s data and test results are applied to the requirements of the FAA’s Airworthiness Directives Manual, Safety
Risk Management Policy, Safety Risk Definition Tables and the
Risk Matrix, it is clear that:
BY THE FAA’S OWN RULES
• The “Likelihood of a Separation” is “Extremely Improbable”
• The “Severity,” of even 2 cylinder separations on the same
engine, is “Minimal”
Based on the facts, the NPRM and proposed AD should be
withdrawn in their entirety.
For more information on the NPRM please visit:
www.ramaircraft.com/nprm.htm.
Thank you,
RAM Aircraft, L.P.
RAM Aircraft, L.P. • 7505 Karl May Drive • Waco Regional Airport • P.O. Box 5219 • Waco, Texas 76708
Phone: (254) 752-8381 • Fax: (254) 752-3307 • e-mail: information@ramaircraft.com • www.ramaircraft.com
©2013 RAM Aircraft, LP TAP092713