Aircraft Thrust-to-Weight & Climb Gradient Resolver

Key Facts

Calculates aircraft thrust-to-weight ratio (T/W) and all-engine initial climb performance.
Solves One-Engine-Inoperative (OEI) second-segment climb gradient compliance per FAR 25.121 and CS-25.
Evaluates climb requirements: 2.4% for twin-engine airframes and 3.2% for four-engine aircraft.
Models density altitude penalties and thrust lapse across elevated or high-temperature airfields.

1. Aircraft & Atmospheric Inputs

Select Aircraft Type Preset:

Takeoff Gross Weight (TOW): 101,000 kg (100% MTOW)

70% Empty-ish 85% Medium 100% MTOW

Airfield Elevation: 0 ft (Sea Level)

Sea Level Denver (5,400 ft) 8,000 ft

Ambient Temperature (OAT): +15 deg C (ISA)

0 deg C +15 deg C (ISA) +30 deg C +45 deg C Hot

Takeoff Thrust Rating:

2. Climb Performance & Compliance

Thrust-to-Weight (T/W) 0.298 All engines rated

OEI Second Segment 3.8% FAR 25 req: >= 2.4%

All-Engine Climb Rate 3,240 fpm Vertical speed at V2

OEI Climb Rate 680 fpm Engine-out climb rate

FAR 25.121 Compliance Assessment

COMPLIANT (1.4% Margin Above Minimum)

The airframe satisfies the certified One Engine Inoperative obstacle clearance criteria with a safe positive climb gradient.

Aerodynamic Parameter Summary

Operating Takeoff Weight: 101,000 kg (222,667 lbs)

Effective Net Thrust: 66,200 lbf (294.5 kN)

V2 Takeoff Safety Speed: 154 KIAS (158 KTAS)

Cleaned Takeoff L/D Ratio: 11.8:1 (Flaps 1/2 Climb)

Commercial Airliner Takeoff Thrust-to-Weight Benchmark

Baseline maximum takeoff thrust and certified MTOW figures across aircraft classes.

Aircraft Model	Engines	Engine Model	Total Thrust	MTOW (kg)	MTOW T/W Ratio	OEI Regulatory Req
Airbus A321XLR	2	CFM LEAP-1A33	66,200 lbf	101,000 kg	0.298	2.4% (Twin)
Airbus A320neo	2	CFM LEAP-1A26	54,240 lbf	79,000 kg	0.312	2.4% (Twin)
Boeing 737 MAX 8	2	CFM LEAP-1B28	58,600 lbf	82,190 kg	0.323	2.4% (Twin)
Boeing 787-9	2	GEnx-1B70	140,400 lbf	254,000 kg	0.251	2.4% (Twin)
Airbus A350-1000	2	Trent XWB-97	194,000 lbf	319,000 kg	0.276	2.4% (Twin)
Boeing 777-300ER	2	GE90-115B	230,600 lbf	351,534 kg	0.298	2.4% (Twin)
Airbus A380-800	4	Trent 970	288,000 lbf	575,000 kg	0.227	3.2% (Quad)

Frequently Asked Questions

What is the second-segment climb gradient in transport category aircraft?

The second segment begins when landing gear is fully retracted at 35 feet above the runway and extends to a minimum of 400 feet above ground level. It represents the most critical obstacle clearance segment following an engine failure at V1.

What are the regulatory minimum climb gradients under FAR 25 and CS-25?

For One Engine Inoperative (OEI) second segment climb, regulations require a gross gradient of at least 2.4% for two-engine aircraft, 2.7% for three-engine aircraft, and 3.2% for four-engine aircraft at V2 speed with takeoff flaps.

Why do twin-engine aircraft typically have higher all-engine thrust-to-weight ratios than quads?

A twin-engine aircraft loses 50% of its total thrust upon an engine failure, whereas a quad loses only 25%. Consequently, twins require excess installed thrust on two engines to satisfy the 2.4% OEI climb gradient requirement.

How does high density altitude affect the climb gradient?

High temperature and high elevation reduce air density, which decreases turbofan mass flow and net thrust while requiring a higher true airspeed (TAS) for V2, compounding the reduction in climb angle.