A useful aircraft strut example is a gas strut supporting a light, upward-opening avionics bay door. It needs to hold the panel open for inspection, avoid overextending the hinge, and close without excessive force. That sounds straightforward, but aviation applications leave little room for a strut that is too strong, too weak or incorrectly mounted.
Before specifying any gas strut for an aircraft, first separate it from the aircraft landing-gear strut. A landing-gear oleo strut is a hydraulic and pneumatic shock-absorbing assembly. A gas strut is a sealed motion-control component used to assist lifting, holding and controlled closing on non-flight-critical items such as access doors, lockers, hatches, covers and some cabin fittings. They perform very different jobs and are not interchangeable.
For certified aircraft, any replacement or modification must follow the applicable maintenance data, approved parts requirements and authorised maintenance procedures. A gas strut may look like a simple hardware item, but changing its force, length or mounting geometry can affect clearances, latching and safe access.
Aircraft Strut Example: an Avionics Access Door
Consider a rectangular avionics access door hinged along its upper edge. The door weighs 8 kg and opens to roughly 100 degrees. When a technician opens it, the gas strut should take most of the weight before the door reaches the fully open position, then hold it securely while inspection work is carried out.
The required force cannot be selected from the door weight alone. The hinge position, centre of gravity, opening angle, strut mounting points and leverage all determine the actual lifting force. If the strut attaches close to the hinge, it has less leverage and needs more force. If it attaches farther from the hinge, a lower-force unit may work, provided there is enough room for the strut body and rod through the full movement.
A correctly selected strut should provide positive support near the open position without making the panel difficult to pull shut. A unit with excessive force may load hinges, distort a thin panel, cause the door to spring open when unlatched, or create an unsafe closing action. One with insufficient force may hold when new but fail to support the panel after temperature changes, wear or added equipment weight.
This is why an aircraft gas strut should be specified from measured geometry, not guessed from a similar-looking unit.
The Measurements That Matter
For a replacement strut, the existing part may provide a useful starting point, but do not rely on markings alone. Confirm the measurements on the installation itself. A replacement needs to match both the physical envelope and the operating load.
Start by measuring the extended length from centre of one mounting point to the centre of the other while the panel is fully open. Then measure the compressed length with the panel fully closed. The difference between those dimensions is the stroke required. A strut must not bottom out before the door reaches its closed position, and it must not reach full extension before the hinge or door stop takes the load.
Record the current force rating, usually marked in newtons with an N suffix. Also identify the end fittings. Ball sockets, eyelets, clevis fittings and brackets are not interchangeable without checking pin size, ball diameter, articulation and available clearance. A fitting that appears to connect correctly can still bind as the door travels.
For a new or custom application, provide the panel weight, overall dimensions, hinge orientation, intended opening angle, mounting-point locations and available space. Photos with a tape measure in view can help confirm the geometry, but they do not replace physical dimensions. A drawing is especially useful where the strut must operate around wiring looms, ducting, frames or nearby equipment.
Force Changes With Position and Temperature
Gas strut force is affected by temperature. A strut may feel firmer on a hot apron and softer in cold high-altitude conditions. That does not mean every application requires a high force rating. It means the specification needs a sensible operating margin across the temperatures the aircraft will experience.
Position also changes the result. In the first part of a lift, the panel may be at its heaviest because the strut has poor leverage. As it opens, the geometry generally improves and the strut becomes more effective. A good installation accounts for that changing load rather than aiming only for a strong hold at full extension.
Orientation matters too. In many gas strut installations, mounting the cylinder uppermost with the rod pointing down when closed helps keep the internal seal lubricated. However, the correct orientation depends on the design, mounting geometry and supplier guidance. Do not reverse a proven arrangement without checking the strut type and clearance through its movement.
Where Gas Struts Are Commonly Used on Aircraft
Gas struts are often suited to non-flight-critical access and convenience applications where controlled support is needed. Typical examples include baggage-compartment doors, service panels, equipment covers, cabin lockers, inspection hatches and ground-support equipment enclosures.
A canopy or large hatch is a more demanding case. It may have a long lever arm, variable wind loading and a serious injury risk if it closes unexpectedly. Here, the load calculation, mounting bracket strength, hinge condition and positive latching arrangement all deserve close attention. A gas strut is an assist device, not a substitute for a correctly designed latch, restraint or approved hold-open mechanism.
The same caution applies to engine cowlings. Heat exposure, vibration, fuel, oil and limited clearance can shorten component life or make a standard strut unsuitable. The application may need corrosion-resistant hardware, suitable end fittings and a strut selected for the actual environment rather than a general industrial equivalent.
Installation Details That Prevent Premature Failure
Poor mounting is a common reason a gas strut fails early. The rod needs to move in line with the strut’s axis. Side loading from misaligned brackets can damage seals and cause sticking or oil loss. Mounting points must be rigid enough to resist repeated opening loads without flexing, cracking or pulling out of a thin panel.
Check that both end fittings can pivot through the full range. A ball joint is useful where the angle changes during travel, while a rigid eyelet can bind if the brackets are not in the same plane. Confirm there is clearance for the cylinder, rod, end fittings and any retaining clips at both ends of travel.
Never drill, heat, cut or attempt to recharge a sealed gas strut. Do not use it as a step, handhold or structural support. If the door or cover must remain open during maintenance, follow the aircraft maintenance procedure and use any required mechanical safety prop or restraint. This is particularly important where personnel may be working beneath the panel.
When a Standard Strut Is Not Enough
A standard gas strut can be suitable where dimensions, force and fittings match a known application. Custom specification is often the better option when the panel is unusually heavy, the mounting space is restricted, corrosion resistance is required or a controlled opening speed is needed.
The trade-off is simple. Selecting from an existing range can be faster where the fit is confirmed. A custom strut takes more information up front, but it can reduce bracket changes, excessive operating force and repeat failures. For fleet, agricultural aviation or specialist equipment work, getting the mounting geometry right before ordering usually saves more time than replacing unsuitable units later.
Gas Struts can help assess dimensions, force requirements and end fittings for suitable non-flight-critical gas strut applications. For aviation work, supply the existing part details and installation measurements, and ensure the final selection and fitment are checked through the appropriate approved maintenance process.
A gas strut should make access safer and easier, not create another point of uncertainty. Measure the installation carefully, respect the operating environment and treat every mounting point as part of the load system.
