Su-25T Flight Test, Section 2, takeoff and landing

[esb77]

This is section 2 of the report from my DCS World Su-25 flight testing program. Flight test programs tend to be fairly huge in terms of data produced and time consumed, so I'm putting sections up as I complete them. Don't worry, you didn't miss section 1, that's the table of contents and introduction, which I didn't think was worth putting up until I've finished the whole report. When it's done I'll put the whole thing up as a unit including section 1. With luck I'll have the thing done before the end of the year.

 

Section 1 also has misc details, like what a 'Standard Atmosphere' is.

 

2 Takeoff and landing

 

 

2.0 Takeoff distances.

 

 

Approximate takeoff roll at maximum gross weight with high drag external stores.

Loadout: Phantsmorgia Elint Pod, KAB 500 kr x 2, A-8 Vikhr x 2, UB 32A 50mm rockets x 2, S-25L x 2, ECM pods x 2, fuel to max weight.

Air temperature 45° C. Elevation 320m.

 

 

Takeoff roll distance:2700m

I.A.S. at liftoff:330 km/h

 

 

Takeoff Roll distance Clean Plane, 3770 kg fuel. Air temperature 45° C. Elevation 320m.

Takeoff Roll: 1500m

 

 

Short strip (1800m runway) takeoff weight limit. Air temperature 45° C. Elevation 40m.

Loadout: A-8 Vikhr x 2, Kh-25ML x 2, R-60 x 2.

Short strip max gross takeoff weight: 16500 kg (36300 lbs) or about 85% gross weight with moderate to low drag external stores. It is recommended that short strip takeoffs be performed with aircraft gross weight of 15500 kg or less.

 

 

2.1 Takeoff abort speeds

 

 

Takeoff abort procedure. Reduce throttle to minimum and wait for turbine r.p.m. to approach 40% then deploy chute. Wheelbrakes may be applied at same time throttle is cut. In borderline cases where ground speed is 60 km/h or less using nosewheel steering to turn the plane may prevent running off of the runway. Be careful not to overdo steering though, or you may drag the wings or damage the landing gear.

 

 

Loadout: Phantsmorgia Elint Pod, Kab500 x 2, A-8 Vikhr x 2, UB 32A 50mm rockets x 2, S-25L x 2, EMC pods x 2, fuel to max gross weight.

 

 

Nalchick 2300 m runway. Standard Atmosphere.

Max weight abort speed limit, dry, wheelbrakes only. 180 km/h

Max weight abort speed limit, dry, chute and wheelbrakes. 270 km/h

Max weight abort speed limit, wet, wheelbrakes only. 180 km/h

Max weight abort speed limit, wet, chute and wheelbrakes. 250 km/h

 

 

Nalchick 2300 m runway. Air temperature -5°C

Max weight abort speed limit, snowy, wheelbrakes only. 190 km/h

Max weight abort speed limit, snowy, chute and wheelbrakes. 270 km/h

 

 

HAZARD NOTICE: When aborting takeoff on a wet/snowy runway use very fine rudder inputs or if possible do not use rudder/nosewheel steering at all. It is very easy to put the plane into a skid with steering inputs on a wet/snowy runway. If in a skid apply gentle counter rudder and release the wheelbrakes, when the skid is under control reapply the wheelbrakes. If the plane starts to experience significant roll it may be best to release rudder and brakes even if this means leaving the runway. If the plane rolls enough that a wing tip touches turf beside the runway loss of both plane and pilot are possible.

 

 

Pilot Comments: It seems quite surprising that wet/snowy runways do not have a great effect on stopping distance during an aborted takeoff. The model seems to assume that conditions are fairly favorable to the pilot in terms of reduced coefficient of friction for between tires and ground for wheelbraking. Despite similar stopping distances it is much more difficult to maintain control of the plane when the runway is not dry. Nalchick has a slightly shorter than average runway. The abort speeds listed should be safe for all of the major Black Sea/Cuacasus theater airfields except Novorossiysk and Gelendzhik.

 

 

2.2 Landing stall speeds.

 

 

Landing stalls speeds may not represent an actual aerodynamic stall. They are the minimum speed in level flight where the plane retains acceptable handling characteristics while in a landing configuration. It is recommended that during an actual landing the aircraft be operated at 10 to 20 km/h faster than the speeds listed here.

 

 

Aircraft configuration: landing flaps, gear down.

 

 

Weapons payload on loaded planes: Phantsmorgia Elint Pod, Kab500 x 2, A-8 Vikhr x 2, UB 32A 50mm rockets x 2, S-25L x 2, EMC pods x 2. 4422 kg weapons.

 

 

Alt 100m

Clean plane 500 kg fuel ___220 km/h

Clean plane 2000 kg fuel __230 km/h

Clean plane max fuel_____ 250 km/h

Loaded plane 500 kg fuel __260 km/h

Loaded plane 2000 kg fuel _270 km/h

 

 

Alt 1000m

Clean plane 500 kg fuel _____220 km/h

Clean plane 2000 kg fuel ____240 km/h

Clean plane max fuel _______250 km/h

Loaded plane 500 kg fuel ___270 km/h

Loaded plane 2000 kg fuel __280 km/h

 

 

Alt 3000m

Clean plane 500 kg fuel _____230 km/h

Clean plane 2000 kg fuel ____240 km/h

Clean plane max fuel _______260 km/h

Loaded plane 500 kg fuel ___260 km/h

Loaded plane 2000 kg fuel __270 km/h

 

 

Pilot comments: Depending on plane loading the Su-25T can retain good control authority down to 180 km/h, however sinkrate becomes excessive before buffeting or departure occur. At minimum controllable speed the vertical component of thrust can have a considerable effect on sinkrate. The pilot should be aware that throttle and AoA have a strong interaction when affecting sinkrate in this portion of the flight envelope. Maneuvering near minimum speeds should be limited to 15 degrees bank at most.

 

 

There are no runways near 3000m elevation in game at present, but if a future module contains theaters in the Andes, Afghanistan, Kashmir, or the Tibetan plateau, the data is here if there's a high altitude runway in the future.

 

 

2.3 No chute landing distance.

 

 

Landing rollout, no chute deployed, dry runway. Elevation 320m.

Clean plane, 1500 kg fuel.

 

 

No chute landing distance: 1700m

 

 

Pilot comments: Under ideal conditions this might be reduced to as little as 1500m, but for a normal landing for most pilots a runway in excess of 2000m is recommended.

Su-25T Flight Test Report_Section2.pdf

Edited August 20, 2013 by esb77