Aircraft model
INTERSTATE S-1A-85F
Everything here is true of every aircraft of the type, not of any one aircraft.
The S-1A-85F is the Franklin-engined Interstate Cadet: the F in the designation denotes a Franklin flat-four in place of the Continental A-65 the specced S-1A carries, at 85 hp. The Cadet is a tandem two-seat high-wing trainer from 1941, built in small numbers before the war ended civil production, and it is best known as the type Cornelia Fort was flying over Pearl Harbor on 7 December 1941.
A Cadet is a light, slow, pleasant aeroplane with a famously low stall speed and excellent visibility, and it is rare enough that owning one means joining the small community that keeps them flying. The Franklin engine is the complication: it is a specialist item with a thin parts supply, and many Cadets have been re-engined to Continental or Lycoming power over the decades. Fabric and tube construction means the recover is the periodic bill and corrosion under the covering is what ends airframes.
Compare with…
Put INTERSTATE S-1A-85F side by side with up to two other models.
- INTERSTATE S-1A-85F
What it is
| Seats | 2 |
|---|---|
| Landing gear | taildragger |
| Engines | 1 |
| Engine | Franklin 4AC-199-D2 |
| Horsepower | 85 hp |
| Fuel | 100LL |
| Certification basis | CAR3 |
| Production start | 1942 |
| Production end | 1942 |
| Endorsements required | tailwheel |
Performance
| Cruise speed | 81 KTAS |
|---|---|
| Range | 300 nm |
| Service ceiling | 14,040 ft |
| Climb rate | 654 ft/min |
| Stall speed (Vso) | 35 KCAS |
| Takeoff over 50 ft | — |
| Landing over 50 ft | — |
Load and fuel
| Seats | 2 |
|---|---|
| Useful load | 425 lb |
| Full-fuel payload | 329 lb |
| Max takeoff weight | 1,200 lb |
| Empty weight | 775 lb |
| Usable fuel | 16 gal |
| Fuel burn at cruise | 4.8 gal/h |
Cost of ownership
| Price, low | $30,000 |
|---|---|
| Price, high | $60,000 |
| Prices as of | 2026 |
| Engine TBO | 1,200 h |
| Overhaul cost, low | — |
| Overhaul cost, high | — |
The fleet and its record
| Registered, all time | 4 |
|---|---|
| Active fleet | 1 |
| Median year built | 1941.0 |
| NTSB events, last 10 years | 0 |
| Fatal events, last 10 years | 0 |
| Events per 1,000 active, last 10 years | — |
| Personal-flying events per 1,000 active | — |
| Ownership transfers, last 24 months | 0 |
| Transfers per 100 active | — |
| Airworthiness directives | 0 |
| Directives, last 5 years | 0 |
| Rate confidence | none |
Peer scores6
| Peer class | Fixed wing single-engine, piston, 1 engine, 1-2 seats |
|---|---|
| Accident record | —1 |
| Severity | —2 |
| Access | —3 |
| Support | 0.8 of 104 |
| Liquidity | —5 |
These record scores treat INTERSTATE S-1A-85F as one design with the same aircraft registered under other names: it includes the record of aircraft once registered under CALLAIR. Prices are not combined.
- Accident record: class median 29.1 · 174 models in class.
- Severity: class median 9.09.
- Access: class median 974.
- Support: class median 81.
- Liquidity: class median 20.47.
- Each of the five categories places the model within its peer class, from 0 (the worst of the class) to 10 (the best): a position among comparable models, not a grade. The overall score is the sum of the categories shown that are scored, out of 10 for each (50 when all five are); it is given only when at least 4 of the five are scored, and it can be set against another model's only when both are in the same peer class and scored on the same categories.