- Brand: Spektrum
- Model Number: SPMSA391
- Product Type: Standard Digital Servo
- Servo Type: Digital
- Servo Size: Standard
- Operating Voltage: 4.8-6.0V
- Shaft Diameter: 4.6mm
- Gear Type: Metal
- Programmable: No
- Water Resistant: No
- Compatible Radio System: Spektrum
Overview
The Spektrum SPM A391 Standard Digital Servo is a reliable and versatile servo solution designed for RC enthusiasts of all skill levels across the UK. Whether you're building your first RC model or expanding an existing collection, this standard digital servo delivers consistent performance and precision control. Digital servos like the A391 offer superior speed and holding power compared to analogue alternatives, making them an excellent choice for RC car UK builds, aircraft projects, and general RC applications where reliable actuation is essential.
As part of Spektrum's trusted servo range, the A391 represents excellent value for money and demonstrates the quality you'd expect from an authorised Spektrum product. This standard-sized servo is engineered to provide the accuracy and response needed for smooth, controlled movements in your RC models. Whether you're a weekend basher enjoying ready to run RC experiences or a dedicated hobbyist fine-tuning your setup, the A391 integrates seamlessly into Spektrum radio systems and works reliably across a wide range of RC applications.
Spektrum is a recognised leader in RC electronics and control systems, and the A391 exemplifies their commitment to delivering quality servos that offer dependable performance for everyday RC use. The servo's standard size makes it suitable for a diverse range of applications, and its digital technology ensures responsive control feedback that helps you get the best from your RC experience.
Key Features
- Digital Servo Technology — The A391 utilises digital servo circuitry rather than analogue, which means faster response times, greater holding torque, and more precise position control, giving you smoother and more accurate movement of control surfaces on your RC model.
- Standard Servo Size — The A391 is a standard-sized servo, making it compatible with a broad range of RC applications and platforms, whether you're working with aircraft, cars, boats or other RC vehicles that require reliable servo actuation.
- 4.8-6.0V Operating Voltage — Operating across the 4.8 to 6.0 volt range means the A391 works reliably with both 4-cell and 6-cell NiMH battery packs as well as 2S LiPo batteries commonly used in RC UK hobby applications, providing flexibility in your power system choices.
- Spektrum Compatibility — As a Spektrum servo, the A391 integrates seamlessly with all Spektrum radio control systems, ensuring reliable signal reception and consistent performance when paired with Spektrum transmitters and receivers.
- Robust Metal Gear Construction — The servo features metal gears that provide durability and strength, resisting wear and maintaining smooth operation through extended use and repeated servo cycles.
Technical Performance
The SPM A391 Standard Digital Servo demonstrates solid engineering designed for reliable everyday use in RC models. As a digital servo operating at 4.8-6.0V, it offers superior performance characteristics compared to older analogue servo technology. The metal gear construction ensures that the servo can handle the demands of regular RC use without premature wear, whilst the digital circuitry provides faster update rates and more responsive control than traditional analogue servos. The standard servo size (4.6mm shaft diameter) is the most common format used across the RC hobby, making the A391 a versatile choice suitable for aircraft applications, RC cars, boats, and numerous other platforms. The servo's ability to operate reliably across the 4.8-6.0V range means it can be powered by standard NiMH packs or modern LiPo batteries, giving you flexibility when configuring your RC model's power system. Whether you're building a ready to run RC setup or customising an existing platform, the A391 provides the holding torque and response speed needed for confident control of your model.
What's in the Box
- SPM A391 Standard Digital Servo
- Servo connector (compatible with Spektrum systems)
- Standard servo hardware and mounting brackets
Frequently Asked Questions
- Is the Spektrum A391 suitable for beginners building their first RC model UK? — Yes, the A391 is an excellent choice for beginners. It's a standard-sized servo compatible with most RC platforms, straightforward to install, and offers the performance benefits of digital technology without unnecessary complexity. If you're building a ready to run RC or assembling your first kit, the A391 will provide reliable control without requiring specialist knowledge.
- What battery voltage does the A391 servo need? — The A391 operates across 4.8-6.0V, meaning it works with both traditional 4-cell and 6-cell NiMH battery packs (commonly used in RC car UK builds) as well as 2S LiPo batteries, giving you several power system options to choose from.
- What makes digital servos better than analogue servos? — Digital servos like the A391 offer faster response times (they update their position more frequently), greater holding torque (they hold their position more firmly against external forces), and more precise control than analogue servos. This means smoother, more accurate movement of your RC model's control surfaces, which translates to better handling and control.
- What is the shaft diameter of the A391? — The A391 features a 4.6mm shaft diameter, which is the standard servo shaft size used across the RC hobby industry, meaning it's compatible with a vast range of servo arms and mounting hardware.
- Can I use the A391 in a Spektrum radio system? — Yes, the A391 is a Spektrum servo and integrates seamlessly with all Spektrum RC radio systems, receivers, and transmitters, ensuring reliable wireless control and consistent performance.
Why Buy from RC Model Shop?
RC Model Shop is a trusted UK RC retailer and authorised dealer for all the brands we stock, including Traxxas, ARRMA, Losi, FTX, Hobbywing, Spektrum and more. Based in Walsall, we have a physical store where customers are welcome to come in, view products and purchase in store. Whether you are a seasoned competitor, a weekend basher, or just discovering the world of RC for the first time, our team of experienced RC enthusiasts is here to help you find the perfect setup and provide ongoing support. Order the SPM A391 Standard Digital Servo Z-SPMSA391 today with confidence, knowing you are buying from an authorised retailer with genuine products, expert knowledge and a commitment to customer satisfaction. Shop online or visit us in Walsall — we look forward to helping you get the most out of your RC experience.
We want to make sure your delivery goes smoothly, so here are some important details about our service:
- For orders above £120, we offer delivery to most mainland UK addresses. For orders under £120, we can still deliver to Northern Ireland and the outlying isles, as long as the item can be sent by Royal Mail, weighs less than 30kg, and fits within 61cm × 46cm × 46cm. Some highland and remote areas may carry an extra delivery charge as couriers often apply surcharges in these locations. If you live in one of these areas, feel free to contact us before ordering so we can confirm the delivery options and costs for you.
- Most of our products include delivery in the price. If your order is under £90, a small delivery fee will apply but do not worry this will always be clearly shown at checkout before you complete your purchase.
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- If your order includes items with different dispatch times we will normally wait and send everything together once all items are in stock. If one of the items is going to take a while we will give you the choice either wait for everything to arrive or let us send the available items now and deliver the rest later. It is up to you.
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- If a product is marked as "Dispatched within 3 working days" delivery usually takes around 3 to 5 working days from when your order is placed.
- For customers in Inverness and other parts of the Scottish Highlands deliveries can take up to 2 working days even if you select next day delivery as couriers do not currently offer a guaranteed next day service to those areas.
