Sooner or later, every propeller pilot hears it: the rising whine of a ducted fan spooling up at the end of the runway. Electric ducted fan (EDF) jets look fast, sound fast and are fast, and they are the most common way into jet flying without the cost and paperwork of a turbine. They are also less forgiving than the trainer that taught you to fly, and the jump between fan sizes is bigger than the numbers suggest.
This guide explains what really changes between 70mm, 80mm and 90mm jets, what you should be able to do before buying one, and how to set up and fly the first flight. Specs come from E-flite's manuals for the Habu STS 70mm, the Viper 70mm and the Habu XS 80mm, which cover three common steps on the jet ladder.
The Short Answer
For most pilots the best first EDF jet is a 70mm model, ideally one with trainer-style stability modes like the Habu STS; 80mm and 90mm jets are heavier, run larger 6S packs, need bigger chargers and smooth runways, and are better as a second or third jet.
- 70mm: the entry point. The Habu STS flies on 3S or 4S; sport 70mm jets like the Viper run 6S 3200mAh.
- 80mm: a big step in weight and power. The Habu XS flies at about 6 lb with a 6S 5000mAh pack.
- 90mm: larger still. Treat it as an experienced-pilot airplane.
- Before your first jet: be smooth with a low-wing aileron plane, consistent on landings, and practiced on a simulator.
1. 70mm vs 80mm vs 90mm: What Actually Changes
Fan diameter is shorthand for the size class of the whole airplane. A bigger fan needs a bigger motor, a bigger ESC and a bigger battery, so everything grows together. Here is how three current E-flite jets compare, straight from their manuals.
| Jet (manual figures) | Fan | Wingspan | Flying weight with recommended pack | Battery | ESC | Suggested first-flight timer |
|---|---|---|---|---|---|---|
| Habu STS | 70mm | 40.5 in (1033 mm) | 3.4 lb (1550 g) | 3S 4000mAh (3S-4S, 3200-4000mAh allowed) | 70 A | 5 min |
| Viper 70mm V2 | 70mm | 43.3 in (1100 mm) | 64 oz (1820 g) | 6S 3200mAh 50C | 85 A | About 3 min |
| Habu XS | 80mm | 48.8 in (1113 mm) | 96.7 oz (2742 g) | 6S 5000mAh 50C (4000-7000mAh allowed) | 130 A | 5 min |
70mm: where most pilots should start
The 70mm class is light enough to forgive a firm landing and small enough to transport easily. The Habu STS is the gentlest option we know of: its manual lists a Beginner mode with self-leveling and stability-assisted takeoff and landing, an Intermediate mode, and an Experienced mode with no limits. It runs on 3S or 4S packs from 3200-4000mAh, and the manual lists 8-10 minutes of flight on a 3S 4000mAh pack. Sport 70mm jets like the Viper step up to 6S 3200mAh packs, flaps and more speed.
80mm: heavier, faster, more battery
The 80mm Habu XS weighs about 6 pounds with its 6S 5000mAh pack, about 1.8 times the Habu STS, and uses a 130 A ESC. More weight means more momentum on landing and more damage when things go wrong. The manual's center of gravity is 125 mm (±10 mm) from the leading edge, checked inverted with the gear down, and it uses a three-position flap setting for takeoff and landing.
90mm: the experienced pilot's class
90mm jets are the largest common foam EDF size, with bigger airframes and battery packs to match. They are impressive, and they demand a pilot who is already comfortable with 70mm and 80mm jets, flaps and retracts. If a 90mm jet is your dream, plan on getting there through a 70mm first.
The hidden costs: batteries and charging
Jets eat batteries. A 6S 5000mAh pack at a 1C charge rate needs about 126 watts of charger output, and charging two at once doubles that. Many basic AC chargers top out around 100 W on wall power. A bigger AC/DC unit like the Hitec RDX2 1000, rated 450 W on AC and 1000 W on DC according to Hitec, keeps a jet session moving. Budget for at least two or three flight packs.
2. Are You Ready for a Jet?
EDF jets do not glide like trainers and they carry speed for longer. That does not mean you need to be an expert, but a few skills should be automatic first.
Skills checklist
- Comfortable with a low-wing aileron plane on high rates, including rolls, loops and inverted flight.
- Consistent landings from a planned pattern, with the throttle as part of the approach rather than idle from far out.
- Orientation at distance: jets cover the sky quickly and look small when they are far away.
- Go-arounds without panic: adding power smoothly and climbing out straight.
- Simulator time on jets: learning the speed and landing picture before you risk a real airframe.
Why the approach is different
A jet's thin wing and swept shape mean it slows slowly and sinks quickly once speed drops. Fly a long, flat final with some power on rather than a steep, idle glide. The FAA's landing chapter describes a stabilized approach: a constant angle, a steady speed and a planned touchdown point, with a go-around if it is not stable. That habit matters more on a jet than on any trainer. The Viper and Habu XS manuals both suggest using high-rate elevator for landings, so you have authority for the flare.
Start with a stability-equipped jet
The Habu STS's Beginner mode is a real safety net for a first jet, and its manual says Intermediate mode automatically switches back to Beginner below about 100 feet. Sport jets like the Viper and Habu XS use AS3X stabilization, which smooths out gusts but does not self-level. A micro jet such as the UMX Viper 30mm is another way to learn jet speed and orientation at a smaller field before a bigger purchase.
3. Setting Up and Flying Your First Jet
The preflight routine is the same as for any new plane, with a few jet-specific details.
Balance it inverted
The Viper 70mm and Habu XS manuals both have you check the center of gravity with the plane inverted and the landing gear down. The Viper's range is 80-90 mm behind the leading edge at the wing root; the Habu STS lists 70-105 mm with 80 mm suggested. Move the battery to adjust, and mark the battery position once it is right.
Set flaps and rates before the field
On jets with flaps, follow the manual's setup exactly, including elevator mix. The Viper's manual lists three flap positions, with an 11% elevator mix on the deployed positions to keep pitch steady. The Habu XS lists 11 mm of flap for takeoff and 35 mm for landing. Fly the first flight on low rate, with high-rate elevator available for landing.
Check the runway and the intake
Jets have small wheels and a fan that pulls air through an intake close to the ground. A smooth paved or short-mown runway makes takeoffs and landings far easier. Keep the intake clear of grass clippings and gravel, and inspect the fan blades before each session.
The first flight
Power up with the throttle at zero (the Habu XS manual notes that AS3X activates the first time throttle passes 25%). Take off into the wind, holding the jet straight with rudder until it lifts off, and climb out gently. Trim at a moderate speed, then fly wide, easy circuits. Set a short timer: about 3 minutes on the Viper (its manual gives 3 minutes in one section and 3:40 in another) and 5 minutes on the Habu STS and Habu XS, per their manuals. Land early with power in reserve, and adjust the timer after you see how much capacity the flight used.
Rules and safety
The AMA's safety code says turbine-powered models must be flown in compliance with AMA's Gas Turbine Program. An electric ducted fan is not a turbine, but the rest of the safety code still applies: fly behind a safety line, avoid flying directly over unprotected people, moving vehicles and occupied structures, and keep powered models at least 25 feet from anyone other than you and your helpers except during takeoff and landing. Jets get far away fast, so stay well inside your field's boundaries.
Conclusion
Start with a 70mm jet, preferably one with trainer modes like the Habu STS, and get comfortable with flat, powered approaches and quick orientation before stepping up. An 80mm jet like the Habu XS is a big jump in weight, battery and charger requirements, and a 90mm jet is best treated as a later goal. Plan for multiple 6S packs and a charger that can keep up, check the CG inverted, and keep the first flights short and high.
Want to see the jets in person or talk through which fan size fits your skills? Stop by our Cumming showroom, browse our jets and EDF collection, or contact the flight desk.
Gear Mentioned in This Guide
E-flite Habu STS 70mm EDF Smart Trainer RTF Basic
A 70mm jet trainer with Beginner, Intermediate and Experienced modes, on 3S or 4S packs.
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E-flite Habu XS 80mm EDF BNF Basic
An 80mm, 6S 5000mAh sport jet for pilots with some jet time.
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E-flite F-16 Thunderbirds 80mm EDF BNF Basic
Scale-look 80mm jet for experienced jet pilots.
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Hitec RDX2 1000 AC/DC Dual Port Charger
Enough charger to keep a pair of 6S jet packs turning over.
Shop nowFrequently Asked Questions
What size EDF jet should I buy first?
A 70mm jet for most pilots. It is lighter, cheaper to run and more forgiving than an 80mm or 90mm jet. A 70mm jet with trainer-style modes, such as the E-flite Habu STS, is the gentlest way in.
Can a beginner fly an EDF jet?
A pilot who has just soloed a trainer should first get comfortable with a low-wing aileron plane. The Habu STS is designed as a jet trainer with Beginner, Intermediate and Experienced modes, which helps, but jets still fly faster and land differently than trainers.
What battery does a 70mm EDF jet use?
It depends on the jet. The Habu STS runs a 3S or 4S pack from 3200-4000mAh, while the Viper 70mm uses a 6S 3200mAh pack. Always use the manual's recommendation so the jet balances correctly.
How long do EDF jets fly?
Usually a few minutes. The Viper 70mm and Habu XS manuals suggest first-flight timers of about 3 and 5 minutes. The Habu STS manual lists 8-10 minutes on a 3S 4000mAh pack.
Do I need a paved runway for an EDF jet?
It helps a lot. Small jet wheels struggle in tall grass, and the fan intake can pick up debris. A smooth paved or short-mown runway makes takeoffs and landings much easier.
Do the AMA turbine rules apply to EDF jets?
The AMA safety code's Gas Turbine Program rule is written for turbine-powered models, and an electric ducted fan is not a turbine. The rest of the safety code still applies, and your club may have its own jet rules, so check with them.
Sources and Further Reading
- E-flite Habu STS 70mm EDF Instruction Manual (Horizon Hobby)
- E-flite Viper 70mm EDF Instruction Manual (Horizon Hobby)
- E-flite Habu XS 80mm EDF Instruction Manual (Horizon Hobby)
- FAA Airplane Flying Handbook, Chapter 9: Approaches and Landings
- Academy of Model Aeronautics Safety Code
- Hitec RDX2 1000 product page
