The Reducer,air Conditioning-Heating, cataloged under National Stock Number 4520-01-278-9931, is classified within Federal Supply Class 4520 (Space and Water Heating Equipment) of the Plumbing, Heating, and Waste Disposal group. The manufacturer of record is Lockheed Martin Corporation Div Rotary and Mission Systems. Government technical data includes 4 specifications, cited from the U.S. Government catalog. The record lists 1 manufacturer part number for this item, enabling identification through both NSN and commercial part number lookups. 2 additional reference documents (drawings, advisory and superseded references) are recorded in the U.S. Government catalog. Current acquisition status: Active.
| Parameter | Value |
|---|---|
| NSN | 4520-01-278-9931 |
| Primary Part Number | 5599989-9 |
| Item Name | Reducer,air Conditioning-Heating |
| FSC / FSG | 4520 / 45 — Space and Water Heating Equipment |
| Manufacturer | Lockheed Martin Corporation Div Rotary and Mission Systems |
| Status | ACTIVE |
| Style Designator | REDUCING |
| Main Trunk Inlet Diameter | 10.880 INCHES NOMINAL IN |
| Fitting Overall Length | 2.260 INCHES NOMINAL IN |
| Main Trunk Reducing Outlet Diameter | 6.000 INCHES NOMINAL IN |
| Acquisition Status | ACTIVE |
| DEMIL Code | DEMIL A — No Demilitarization Required |
| Hazard | No hazard code in the DLA record (HMIC N) |
| Criticality Code | X |
| Part Number | Manufacturer |
|---|---|
| 5599989-9 PRIMARY | Lockheed Martin Corporation Div Rotary and Mission Systems (USA) |
| Reference | Meaning |
|---|---|
| 5599989-9 | C/1 Advisory reference — outside the item-of-supply concept Naval Sea Systems Command |
| 5599989 | D/9 Drawing number reference only Naval Sea Systems Command |
NSN 4520-01-278-9931 is a Reducer,air Conditioning-Heating, manufactured by Lockheed Martin Corporation Div Rotary and Mission Systems, classified under FSC 4520, Space and Water Heating Equipment. Status: active.
NSN 4520-01-278-9931 has 1 manufacturer part number on file: 5599989-9 (Lockheed Martin Corporation Div Rotary and Mission Systems).
Key specifications for 5599989-9: Style Designator: REDUCING; Overall Length: 12.880 INCHES NOMINAL IN; Overall Width: 5.960 INCHES NOMINAL IN; Main Trunk Inlet Diameter: 10.880 INCHES NOMINAL IN. 4 specifications are documented in the U.S. Government catalog.
No hazard code in the DLA record (HMIC N). Hazard information on this page is shown exactly as it appears in the DLA record.
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-16.
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-18.