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Manufacturer Hamilton Standard Propeller Co.
Aircraft Numerous (See List Below)
Propeller Models 23E, 24D, 33E Hamilton Standard Hydromatic Propellers
Part Number 52478, 52478-1
Proper Description SEAL – DOME & BARREL
AirCorps Aviation PMA Part Number 52478-ACP, 52478-1-ACP
NOW PMA APPROVED BY AIRCORPS AVIATION / AIRCORPS DEPOT
No pilot or mechanic wants hydraulic fluid being slung by the propeller onto the engine or cowlings, or worse yet compromising visibility by coating windscreens. Propellers are becoming rarer and more costly, it isn’t uncommon to now see warbird props that are six figures. Proper maintenance and upkeep amid dwindling and aging parts supplies present long term challenges for our industry. Notably rubber parts produced 70-80 years ago have become rigid and embrittled; these common wear items and consumables are used extensively on props and accessories. AirCorps Aviation in Bemidji MN has found a niche in producing rubber parts, notably seals and dynafocal engine mounts for a variety of warbirds including the P-51, B-25, B-17, P-47, P-38, Wildcat, TBM, and more. The recent PMA of the 52478 and 52478-1 dome seal for 23E, 24D, and 33E series Hamilton Standard Hydromatic propellers represents the first propeller part under the FAA-PMA quality system at AirCorps Aviation. Read on to learn why we produced this seal and how this seal, produced with the original Hamilton Standard drawing, meets the dimensional specs required at installation …
Hamilton Standard Dome and Barrel Seal, or simply: Dome Seal, can be found on most WWII era Hamilton Standard propeller & hub assemblies. The oil seal between the barrel assembly and the dome assembly is formed by a compression type dome-barrel seal which seats between the inner diameter of the outboard barrel half (just inboard of the dome retaining nut). This trapezoidal shaped circular seal is stretched around the bottom of the fixed cam and installed between the Dome assembly and barrel assembly. This seal is available in two sizes, standard size and .025 oversized, and is responsible for retaining hydraulic fluid (in this case engine oil) inside of the propeller hub assembly.
Hamilton Standard Propeller Co. designed the 52478 – Seal – Dome & Barrel on May 28, 1937. The drawing was altered / revised a number of times into 1947.
Critical to the design and function of the AirCorps FAA-PMA seal is that the height and width dimensions must be inspected when installed and stretched over a mandrel.
When the propeller dome is installed on the hub assembly, the preload between the cam gear in the dome and the blade gears on the propellers is controlled by the distance from the bottom face of the dome to its mating surface on the hub. Maintainers can adjust this height, and therefore adjust preload, to account for wear by using thin donut shaped shims to space the dome from the hub assembly.
The P-51 maintenance manual AN 01-60JE-2 page 181 provides guidance on how to do this as do other aircraft and Hamilton Standard maintenance manuals. The notes under figure 227 of AN 01-60JE-2 give reference to usage of the 52478-1 oversized dome seal.
The oversized seal (52478-1) is used when the total width of preload shims under the dome assembly exceeds .025″.
Hamilton Standard Propellers were furnished with both the stock 52478 & 52478-1 dome barrel seals. AirCorps recommends operators, and maintainers stock both seals.
This pair of seals can be purchased here. (52478-SET)
This critical seal on the propeller requires inspection for cracks, pliability, and attention to prevent failure and leakage.
Some key questions in determining if your propeller seals needs to be inspected / tested / replaced / repaired:
AirCorps recommends these additional inspections / actions.
New surplus and replacement seals are now typically over 70 years old and have a propensity to harden and be undersized when installed.
How to inspect – Visual Inspection
Tolerance of damage or wear : Zero
Solutions offered: Replacement of Seal
The AirCorps Aviation FAA-PMA dome seal was designed to be identical to the original dome seals as no deficiencies in the OEM design have been noted. With that said, reverse engineering a component from a 1940’s era drawing can bring out its own challenges.
Where Used – Hydromatic Hamilton Standard Propeller Models: 23E50, 24D50, 33E60
Hamilton Standard 23E50 Propellers:
23E50-107, 23E50-109, 23E50-119, 23E50-137, 23E50-155, 23E50-163, 23E50-179, 23E50-181, 23E50-189, 23E50-231, 23E50-233, 23E50-241, 23E50-247, 23E50-285, 23E50-287, 23E50-301, 23E50-311, 23E50-315, 23E50-321, 23E50-327, 23E50-389, 23E50-391, 23E50-393, 23E50-399, 23E50-455, 23E50-471, 23E50-473, 23E50-473, 23E50-489, 23E50-491, 23E50-495, 23E50-505, 23E50-543, 23E50-591, 23E50-797
Hamilton Standard 24D50 Propellers:
24D50-65, 24D50-71, 24D50-87
Hamilton Standard 33E60 Propellers:
33E60-13, 33E60-15, 33E60-31, 33E60-33, 33E60-35, 33E60-79, 33E60-85
Hamilton Standard Dome Assemblies:
59627, 59626, 54053, 55011, 55316, 54776, 55290, 57990, 55288, 59468, 59632, 61144, 59648
52478 & 52478-1 PROP DOME SEALS ARE COMMONLY INSTALLED ON THESE AIRCRAFT
| AIRCRAFT | PROPELLER MODEL | BLADE NUMBER |
| P-51 MUSTANG | 24D50 | 6523 & 6547 |
| B-17 FLYING FORTRESS | 23E50 | 6477 |
| B-24 LIBERATOR | 23E50 | 6477 |
| B-25 MITCHELL | 23E50 | 6477 & 6359 |
| C-47 SKYTRAIN | 23E50 | 6477 |
| C-53 SKYTROOPER | 23E50 | 6477 |
| DOUGLAS DC-3 | 23E50 | 6477 |
| C-54 SKYMASTER | 23E50 | 6507 |
| PBY CATALINA | 23E50 | 6353 |
| F4U, AU-1, FG-1D CORSAIR | 23E50 | 6525 |
| F6F HELLCAT | 23E50 | 6541 |
| TBM AVENGER | 23E50 | 6359 |
| LOCKHEED VENTURA | 23E50 | 6477 |
| SBD DAUNTLESS | 23E50 | 6511 |
| A-20 HAVOC / BOSTON | 23E50 | 6353 |
| A-26 INVADER | 23E50 | 6359 |
| C-82 PACKET | 33E60 | 6491 |
| C-69 CONSTELLATION | 33E60 | 6491 |
AirCorps Aviation has PMA approval for 52478-ACP and 52478-1-ACP Seal – Dome and Barrel. Hamilton Standard Propellers were furnished with both the stock 52478 & 52478-1 dome barrel seals. AirCorps recommends operators, and maintainers stock both seals.
AirCorps can provide parts and answer questions related to this seal. AirCorps Depot also maintains a growing inventory of Hamilton Standard prop parts to support the continued airworthiness of airframes and propellers.
Contact Eric Trueblood for more information – erict@aircorpsaviation.com
52478-SET
(QTY 1) 52478-ACP & (QTY 1) 52478-1-ACP
Seals – Dome and Barrel – STD and .025
PMA APPROVED
52478-ACP
(QTY 1) 52478-ACP
Seal – Dome and Barrel
PMA APPROVED
52478-1-ACP
(QTY 1) 52478-1-ACP
Seal – Dome and Barrel – .025 Oversized
PMA APPROVED
Andy Smude
Engineering Manager
Contact us for more info on ways we can assist with your project!
Ryan Maier is AirCorps Aviation’s certification engineer who completed his Bachelors of Mechanical Engineering at NDSU in 2021. He has a background in aircraft integration through certification of Cloud Seeding and Atmospheric Research aircraft in North Dakota. Ryan is able to live his passion every day as part of the AirCorps team while researching original technical data to generate new PMA products to support and preserve the warbird Industry. Ryan owns and operates a Luscombe 8A and is continually invested in learning, supporting, and engineering historical aircraft.
Contact us for more info on ways we can assist with your project!
Ryan Maier
Certification Engineer
AirCorps Library – Hamilton Standard Resources
AirCorps Library – P-51 Mustang Resources
AirCorps Library – 23E50 Resources
AirCorps Library – 24D50 Resources
AirCorps Library – 33E60 Resources
Aircraft Inspection & Maintenance Guide – P-51, 00-2
Aircraft Inspection & Maintenance Guide – P-51, 00-20A-2-P-51, 7-Nov-1947
Maintenance Instructions – Cavalier Mustang – F-51D, T.0. 1F-51D-2, 27-Sept-1968
WHILE AIRCORPS BELIEVES THAT THE INFORMATION CONTAINED THEREIN IS ACCURATE AND CORRECT, AIRCORPS DOES NOT WARRANT THE ACCURACY OR THE CORRECTNESS OF ANY DRAWINGS, MANUALS, OR THE INFORMATION (COLLECTIVELY THE “INFORMATION”) CONTAINED THEREIN. THE INFORMATION, DRAWINGS AND REFERENCE MATERIAL ARE SUPPLIED TO THE CUSTOMER ON AN “AS IS, WHERE IS” BASIS, WITH NO WARRANTY OR REPRESENTATION OF ANY KIND. VENDOR MAKES NO WARRANTIES, EITHER EXPRESS OR IMPLIED, WITH RESPECT TO MERCHANTABILITY OR FITNESS APPLICABLE TO THE INFORMATION, INCLUDING WITHOUT LIMITATION WARRANTIES AS TO THE ACCURACY OF THE INFORMATION, CONDITION, VALUE, MERCHANTABILITY, OR FITNESS FOR ANY PARTICULAR PURPOSE, WHETHER ARISING BY OPERATION OF LAW, COURSE OF DEALING OR USAGE OF TRADE, ARISING AT LAW OR IN EQUITY OR OTHERWISE. YOU ACKNOWLEDGE THAT YOU ARE NOT RELYING UPON ANY STATEMENT OR REPRESENTATION OF SELLER REGARDING THE INFORMATION. YOU AND VENDOR HEREBY EXPRESSLY WAIVE ANY CLAIM FOR INCIDENTAL, SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES, INCLUDING DAMAGES RESULTING IN PERSONAL INJURY AGAINST THE OTHER, AND WILL NOT BE LIABLE TO THE OTHER PARTY IN CONNECTION WITH THIS AGREEMENT UNDER ANY THEORY OF LIABILITY FOR ANY INCIDENTAL, SPECIAL, INDIRECT, PUNITIVE OR CONSEQUENTIAL DAMAGES OF ANY KIND, INCLUDING WITHOUT LIMITATION, ANY SUCH DAMAGES ARISING FROM BREACH OF CONTRACT, BREACH OF WARRANTY, NEGLIGENCE OR STRICT LIABILITY. ALL WORK SHOULD BE COMPLETED IN ACCORDANCE WITH FAA REGULATIONS AND APPROVED DATA.
