Buyer's guide

Buying an aircraft hydraulic pump or valve: part number, mod status, condition, release remarks and fluid type

By the MG AVIATION TECH team · Published · 9 min read

An engine-driven pump, an AC motor pump, a power transfer unit or a selector valve is a rotable: it is overhauled and reused, and it is usually quoted overhauled rather than new. The part number is only the start: the dash number, modification status, serial number, release remarks and the fluid the unit was built for all decide whether it fits your aircraft. This guide takes them in order and ends with a checklist to use before the PO.

What you are buying: pumps, PTUs and valves

The FAA's airframe handbook for maintenance technicians describes the power sources on a modern aircraft as a combination of engine-driven pumps (EDP), electric motor-driven pumps, air-driven pumps, power transfer units (PTU) and pumps driven by a ram air turbine. As a general rule, it says, the electric pumps are for emergencies or ground operation. A PTU transfers power between two hydraulic systems, but not fluid. Downstream of the pumps sit the valves: check valves, relief valves, selector valves, shutoff and priority valves.

For a buyer they share three traits: they are serialized and repairable, so the unit has a history; they come in several dash numbers and modification states; and they are built for one fluid. The same logic, minus the fluid, applies to rotable valves outside the hydraulic system, such as a cabin pressure outflow valve.

From our quote data

Pumps, valves and actuators are the largest named category among the lines our customers have ordered from us. In supplier quotes we received between June and September 2026, lines for pumps (71 part numbers) were offered overhauled about 49% of the time, new about 25% and serviceable about 10%. Lines for valves (338 part numbers) were 36% new, 35% overhauled and 11% serviceable. Fasteners, for comparison, were offered overhauled on 0.1% of lines.

Pin down the exact part: data plate, IPC and CMM

Collect the identity of the unit coming off the aircraft and of the ones the aircraft accepts. They are not always the same.

  • Data plate of the removed unit. Part number with dash number, serial number and any modification markings. Many units carry two part numbers: the component maker's and the airframe manufacturer's.
  • The aircraft's IPC. It lists the part numbers approved at that position, for that aircraft's effectivity, with any alternates. The IPC is what makes a part installable, not a match on the basic number.
  • The unit's CMM. The component maintenance manual defines the configurations, the modifications that change the dash number, and the test the unit must pass after overhaul.

A real example of the two numbers: FAA airworthiness directive 2017-18-11, on the Textron (Beechcraft) Model 390, names the engine-driven pump as P/N 66179-01 (Beechcraft/Textron P/N 390-389022-0003). Put both numbers on your RFQ when you have them. A stock list may carry either one.

For a unit marked with more than one part number, FAA Advisory Circular 43-9D says the part number on the return to service should typically match the customer's work request. If you need the release to show a particular number, say so.

If you accept other part numbers, say which; how to write that on an RFQ is in our interchangeability guide.

Modification status, service bulletins and ADs

Two units with the same part number are not necessarily equivalent. A service bulletin can change a unit with or without changing its dash number, so ask for the SB status of the unit on offer and compare it with what your engineering requires.

Airworthiness directives can reach down to individual serial numbers. In the AD cited above, the unsafe condition was one manufacturing lot of EDPs with pitting in the aluminum port caps, which could lead to fatigue cracking and loss of fluid. The AD identified affected pumps by serial number, through a table in the pump maker's service bulletin, and required a replacement pump that was either not in that table or reworked per the bulletin. Every pump involved had the same part number; only the serial number and the SB record told them apart.

So, for each pump or valve line, ask for:

  • the serial number of the unit being offered, before the PO;
  • the service bulletins embodied, and ADs complied with, with their revision;
  • whether the release remarks state them (next section).

Condition: what NE, OH, SV, AR and exchange mean for a rotable

The codes are the same for every part and are defined in our condition codes guide. What changes with a pump or valve is how you weigh them.

OfferWhat it usually means for a pump or valveAsk
NE (new)Straight from the maker or its distributor, current configurationLead time; whether "new surplus" has sat in storage and for how long
OH (overhauled)Full work scope to the CMM; the normal offer for a rotableWhich shop, which CMM revision, date of overhaul, test results, SBs embodied
SV (serviceable)Released after less than an overhaul: often repaired, or inspected and testedBlock 11 wording and what was actually done; time since last overhaul if known
AR (as removed)Not installable; a core for your own repair or exchangeRemoval reason, non-incident statement, why it came off
ExchangeA serviceable unit now against your removed unit laterCore terms, BER basis, over-and-above charges

SV deserves the most questions. AC 43-9D defines "OVERHAULED" as at least disassembled, cleaned, inspected, repaired as necessary, reassembled and tested to approved data, while "INSPECTED" or "TESTED" means examination or measurement to a standard, such as a bench test. A unit that passed a bench test and one that was overhauled are both serviceable, but they are not the same product.

If you already have a removed unit, you are choosing between repair and replacement as much as between conditions: see repair or replace an aircraft component. If you take an exchange, the terms that settle the final bill (core deadline, BER, over-and-above charges) are in our exchange guide.

What the 8130-3 should say for an overhauled pump or valve

For a unit returned to service after maintenance in the US, the usual release document is FAA Form 8130-3, completed per AC 43-9D. (Whether you need it, an EASA Form 1 or a dual release is covered in 8130-3 vs EASA Form 1.) Two blocks carry most of what a buyer needs:

  • Block 11, status/work: OVERHAULED, REPAIRED, INSPECTED and/or TESTED, or MODIFIED. AC 43-9D notes that the applicable standard must be described in block 12.
  • Block 12, remarks: the work performed and the results the installer needs, directly or by reference to supporting documents.

AC 43-9D lists what block 12 may include, depending on the form's purpose. For a pump or valve bought overhauled, these are the ones to look for:

  • the data used for the work with its revision level, for example the CMM and its revision;
  • compliance with ADs or service bulletins;
  • repairs and modifications carried out, and replacement articles installed;
  • any PMA parts used (the AC notes that some EASA-based air carriers do not accept PMA parts, and recording them warns the end user before installation);
  • references to work orders or shop travelers used for the work, and attachments, which should carry the form's tracking number.

A block 12 that says only "overhauled" with no data reference gives you nothing to check against your requirements. Ask to see a copy of the 8130-3 before the PO; our tag date guide covers how old that form may be.

Also ask for the shop's work order or teardown findings and the test results. A trade-press article from 2000, describing a pump maker's overhaul shop, quoted that maker's definition of an overhaul as replacing all bearings, all springs and all soft goods, and described the pump being run to its test specification with the performance recorded. Definitions differ between makers and CMMs; the documents matter more than the word on the quote.

Time since overhaul and shelf time

The same 2000 article described hydraulic pumps as maintained "on-condition": they stay in service as long as they produce the required pressure, and with clean fluid can run for about 20,000 hours or more between overhauls. So "time since overhaul" is not a hard limit for most pumps, but it is still information worth having:

  • For an SV unit: hours or cycles since the last overhaul, if recorded.
  • For an OH unit that has been in stock: the overhaul date against today. No FAA rule sets a maximum age for the 8130-3 itself, but your own quality system or your customer may. Whether a unit that has been stored needs a re-test before installation is a question for the CMM and your quality department. Ask the seller for the overhaul date and how the unit was stored: capped ports, preserved, in its container.

Hydraulic fluid: mineral oil or phosphate ester

Most commercial transport aircraft use fire-resistant phosphate ester fluids (Skydrol and Hyjet are trade names; SAE AS1241 is the specification). Small aircraft, the handbook says, predominantly use mineral-oil fluid to MIL-H-5606 (now MIL-PRF-5606), and some have switched to the fire-resistant polyalphaolefin fluid MIL-H-83282, which uses the same seals. The FAA handbook is blunt about mixing them: petroleum-based and phosphate ester fluids "will not mix", and neither are the seals for one fluid usable with or tolerant of the other. Seals for mineral-oil systems are neoprene or Buna-N; seals for phosphate ester systems are butyl rubber or ethylene-propylene. A system serviced with the wrong fluid must be drained and flushed.

For a buyer that means:

  • Confirm the fluid for the unit on offer. The seal material is part of the configuration. Ask which fluid the unit was built or overhauled for, and which fluid it was tested in.
  • Ask what it is shipped in. For mineral-oil systems, the handbook notes that suppliers generally ship hydraulic components with MIL-H-6083, a rust-inhibited version of MIL-H-5606 that is interchangeable with it. That note covers mineral-oil systems only; for a phosphate ester unit, ask the seller what the unit was preserved with, and follow the CMM and your maintenance data on installation.
  • Treat a cross-fluid unit as the wrong part, not a bargain. Whether it can be converted is for the shop and the CMM to decide.
  • Send the core with the right history. If your removed pump failed and shed debris, tell the shop. The same 2000 article recounts a pump maker's overhaul shop finding a piece of wire from a filter's mesh in a pump intake and telling the airline, whose hydraulic filter turned out to be coming apart; without that warning, the shop said, the replacement pump and other components could have been damaged. The handbook's flushing procedure replaces the system filters and circulates clean, filtered fluid until inspection of the filters shows no obvious signs of contamination. Whether your aircraft needs that is for your maintenance data to decide; better to know before the pump arrives.

Seal compatibility applies to the O-rings and packings you order with the pump, too. Check the seal part numbers in the IPC or CMM rather than choosing by size.

Checklist: what to ask before the PO

ItemPut in the RFQGet before the PO
Part numberMaker's and airframe manufacturer's P/N with dash, from the data plate and IPCThe P/N on the unit and on its release, matching what you asked for
AlternatesWhich alternates, if any, your engineering acceptsWritten confirmation of which number is being offered
Mod / SB statusSBs you require embodiedSB list for the unit, with revision
ADsAircraft type and effectivitySerial number of the offered unit and AD compliance
ConditionConditions you accept, e.g. "OH, SV acceptable" or "exchange and outright"Block 11 wording on the release
Release8130-3, EASA Form 1 or dual releaseCopy of the form; block 12 naming the CMM and its revision, SBs, repairs, PMA parts
Work recordAsk for teardown findings and test resultsWork order or teardown report, test data sheet
AgeAny tag-age limit you applyOverhaul date; storage and preservation
FluidYour system's fluidThe fluid the unit was built, overhauled and tested for
TraceThe trace you needTrace documents and, for used units, the non-incident statement
ExchangeYour core's P/N, dash, mod status and removal reasonCore deadline, BER basis, over-and-above terms in writing
From our quote data

In supplier quotes we received between June and September 2026, about 39% of pump lines and 32% of valve lines stated an 8130-3, and about 25% and 18% an EASA Form 1 (dual releases count in both). On about a third of pump lines and 45% of valve lines, no certificate was stated at all, and traceability was stated on about 61% of pump lines and 51% of valve lines. A line without a stated release is common. Ask; do not assume.

If the RFQ comes to us, each line comes back with condition, certificates, lead time in days, minimum order and, where the supplier states it, the ships-from country. When you order in our client portal, you can tick "certificate needed" per line and add a note, which is the place for the fluid, SB status and serial number questions above.

Send the pump or valve line as you have it

Email the part number, dash number and the conditions you accept to [email protected], in the file you already have: Excel, PDF, a scan or the email body, five lines or five hundred. Your inquiry will be reviewed by a specialist within one business day. Prices are Ex Works our warehouse in Orlando, FL, and the cost of bringing a line to Orlando is shown separately, per line, in the portal.

Send your RFQ →

Our client portal, RFQ Radar, keeps every quote, order and invoice in one place.

Before you buy, check what certificates and trace come with each part. Aircraft on ground? See how our 24/7 AOG desk works.

Sources

All checked on 24 September 2026.