Cessna 340 vs Rockwell Commander 685

Side-by-side specs, range, and operating costs.

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Dimensions & configuration

Representative planforms, drawn to shared scale.

Cessna 340
38 ft × 34 ft ⭥ 13 ft
2× Piston Retractable Pressurized
Rockwell Commander 685
47 ft × 42 ft ⭥ 14 ft
2× Piston Retractable Pressurized

Flight Profile

Service ceiling, range, and climb rate.

Tap legend to isolate

Arc represents the climb-cruise-descent profile based on published service ceiling and range. Climb rate annotated on ascent. FL180 (18,000 ft) shown for reference.

Mission Performance

Stall, approach, cruise, range, ceiling and climb: best values are at the top.

Mission performance specifications
Specification Cessna 340Rockwell Commander 685
Stall speed 79 kt81 kt
Approach speed 100 kt106 kt
Cruise speed 229 kt222 kt
Range 1406 nm1251 nm
Service ceiling 29800 ft25000 ft
Rate of climb 1650 fpm1490 fpm
Fuel burn 38.0 gph45.0 gph

Each axis is scaled independently across the compared aircraft and printed in its own units; every vertex sits at the published figure. Higher is better on all axes: Stall, Approach and Fuel Burn are inverted (lower = higher). A missing figure breaks the line at that axis.

Fuel Burn & Range

Range, endurance, and what the fuel costs by the hour.

Cessna 340 Avgas
38.0 gph
Baseline
1,406 nm range 6.0 nm/gal 203 gal usable $247 fuel/hr 5h 20m endurance
Cessna 340: 38.0 gph at cruise, 1,406 nautical mile published range, 5 hour 20 minute endurance, 6.0 nautical miles per gallon.
Rockwell Commander 685 Avgas
45.0 gph
Baseline
1,251 nm range 4.9 nm/gal 256 gal usable $292 fuel/hr 5h 41m endurance
Rockwell Commander 685: 45.0 gph at cruise, 1,251 nautical mile published range, 5 hour 41 minute endurance, 4.9 nautical miles per gallon.
Avgas range each cell = 1 hr of cruise · width scales with speed tank-dry · at this cruise burn

Bars show published still-air range: select a cell to view cruise-hours and fuel usage. Endurance is full tank at the displayed cruise burn rate; the extra is reserve and economy margin. Estimates only. Always verify against the POH.

Runway Performance

Density altitude adjusted estimates

Outside Air Temp
0°F57°F115°F
Field Elevation
SL4,0008,000 ft

Takeoff over 50 ft obstacle

Landing ground roll

Density Altitude

Monte cristo

Base distance DA penalty
Scale: 6,000 ft

FAA 10%/1,000 ft DA rule of thumb (FAA-H-8083-25B). Turboprops and jets are less sensitive in practice. Always verify against the POH.

Estimated Operating Costs

Hourly direct and annual fixed costs

Scale:
Cessna 340 Avgas
$481 /hr
Baseline
Cessna 340: $481 per flight hour — fuel $247, maintenance and reserve $234.
Rockwell Commander 685 Avgas
$661 /hr
Baseline
Rockwell Commander 685: $661 per flight hour — fuel $292, maintenance and reserve $369.
Cessna 340 Piston
$21,000 /yr Baseline
Cessna 340: $21,000 per year — insurance $7,500, hangar $7,200, annual inspection $6,300.
Rockwell Commander 685 Piston
$18,900 /yr Baseline
Rockwell Commander 685: $18,900 per year — insurance $6,000, hangar $5,400, annual inspection $7,500.

Estimates only. Hourly direct operating cost, based on fuel price and reserves; Annual fixed costs (insurance, hangar, and inspection). Costs vary by location, pilot profile, and market conditions. See individual aircraft pages for source notes.

Capability & limits

Payload vs useful load limit

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Cessna 340 Piston
6 / 6 seats 203 gal / 203 gal fuel 861 lbs wet payload 2,079 lbs useful 5,990 lbs MTOW
Rockwell Commander 685 Piston
8 / 8 seats 256 gal / 256 gal fuel 1,493 lbs wet payload 3,029 lbs useful 9,000 lbs MTOW

Shows selected occupants against full fuel, within the aircraft's useful-load limit. Fuel weight at 6.7 lb/gal jet-A, 6.0 lb/gal avgas; pax and luggage are 190 + 30 . Change payload weights in global settings.

Payload-Range Map

Origin: · two fingers to move map

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