1. EAGLE TT AND USATS AWD AIRCRAFT
TRACTORS TECHNICAL BRIEF
Manufacturing since 1969
2. Why are Eagle aircraft tractors superior to any other tractor for
military aircraft towing?
Commercial Products – With 20 years of experience of continuous product
improvements, Eagle aircraft tractors have unequalled reliability; which is
reflected in the only 3-year/3,000 hr warranty on the market.
All Wheel Drive (AWD) – With equal weight distribution, Eagle AWD aircraft
tractors weigh 1/3 less than RWD tractors. This makes Eagle aircraft tractors a
better option for air transportability and operation on unimproved surfaces.
Designed as Aircraft Tractors – Eagle aircraft tractors were designed from the
ground up specifically to move aircraft. Most other tractors in the industry were
designed to tow baggage or other GSE. Eagle Tugs designs its aircraft tractors
using precise Drawbar Pull (DBP) calculations and testing, assuring that its
aircraft tractors are rated correctly to move each load.
On the needs of the Military, First Sergeant JT Lee, 160th Soar:
“As a military vehicle it has to be air-liftable,” and, “It has to be able to go into
3. Aircraft Tractor Design
NATO STOCK NUMBER 1740 01 461 4279
Example of low profile design and direct Example of the ergonomic design (easy
hitch view of the Eagle AWD TT-series. ingress/egress) of the Eagle AWD USATS-6
4. Military Aircraft Towing
This Technical Brief explains the details behind the design features
of Eagle aircraft tractors which make them superior for military
1. All Wheel Drive (AWD) vs. Rear Wheel Drive (RWD) –
Discusses the operational differences as they pertain to aircraft
2. Drawbar Pull (DBP) – Discusses how drawbar pull is calculated
and how it applies to military aircraft towing. The proper method
to DBP testing is also discussed.
3. Aircraft Tractor vs. Baggage Tractor – Discusses the
operational differences between an Eagle aircraft tractor and a
baggage tractor, and why Eagle aircraft tractors are the best
option for military aircraft towing.
5. All Wheel Drive (AWD) vs. Rear Wheel Drive (RWD)
The 2 major benefits of AWD aircraft tractors when moving military
1. AWD aircraft tractors weigh 1/3 less than RWD tractors and still
achieve the same towing capacities.
a. Less weight is better for air transportability
b. Less weight is better for operating on unimproved
2. With equal weight distribution, there is no loss of steering with
AWD aircraft tractors as with RWD tractors which tend to be too
light in the front end.
6. Proven in theater operations: Below Afghanistan
7. All Wheel Drive (AWD) vs. Rear Wheel Drive (RWD)
To better understand the advantages of AWD, the following physical laws
must be defined:
Tractive Effort (TE) – The force that a tractor is able to deliver to the
concrete through its wheels.
Coefficient of Friction – The ratio of the force required to initiate Tractive
Effort (TE) with regards to the weight over the tractor drive tires.
The ratio is .90 for pneumatic rubber tires on dry brushed concrete,
which means that 90% of the available power is transferred to the
concrete to move the load.
Drawbar Pull (DBP) – The measurement of smooth lineal force resulting
from the rated Tractive Effort (TE), adjusted by the Coefficient of
8. All Wheel Drive (AWD) vs. Rear Wheel Drive (RWD)
Proper weight distribution above a tow tractor’s drive wheels is calculated as follows:
RWD – Must have an equal amount of weight over the tractor’s drive wheels as the
required amount of Tractive Effort (TE) force. Also, in order maintain effective
steering, the front steer-axle must weigh at least ½ the weight of the rear axle.
- A lineal pulling force of 8,800# TE multiplied by .9 COF = 8,000# DBP. So, in order
to develop 8,000 lbs. DBP, a RWD tractor must weigh 8,800# over its drive wheels
(rear axle only). Additionally, in order to maintain effective steering, the front steer-
axle must then weigh 4,400#. The result is that an 8000# DBP, RWD tractor must
AWD –An AWD aircraft tractor needs 8,800# over its drive wheels, but since both
axles are drive axles, the total weight needed for an AWD aircraft tractor is 8,800#.
Also, the weight to maintain effective steering is also accomplished with ½ the
tractor’s weight over front steer-axle. The result is that an 8,000 DBP, AWD
tractor must only weigh 8,800#, or 1/3 less than a RWD tractor generating the
9. YANMAR DIESEL ENGINES
TIER 1 & TIER 2
10. All Wheel Drive (AWD) vs. Rear Wheel Drive (RWD)
Proper weight distribution above a tow tractor’s drive and steer wheels
also assure proper, safe steering.
- Most RWD tractors do not demonstrate the necessary 2/3 weight over
the drive wheels, and 1/3 weight over the steered wheels, which at times
may result in a lifting of the front steered wheels, and a loss of traction.
Even with proper weight distribution, pushing at angles beyond 45
degrees with RWD tractors results in a right or left skid challenge, caused
by the doubled weight of the rear drive axle. Due to the fact that the rear
drive axle generates all of the Tractive Effort (TE), it tends to overpower
- AWD drive aircraft tractors exhibit none of these steering problems.
With equal weight distribution over front and rear drive wheels, AWD
aircraft tractors naturally overcome the resistance caused by turning an
aircraft beyond 45 degrees.
11. The only Aircraft Engineered AWD Tractors in this weight class.
AWD allows for even chassis weight distribution for greater control and smooth pushbacks.
12. Drawbar Pull (DBP) and Proper Testing
Eagle Tugs prides itself on its 40 plus years of designing and
manufacturing tow tractors. This experience has helped us to design tow
tractors that are weighted and powered appropriately to push or pull their
required and marketed weights.
A key to our design is how we calculate our tow tractors’ towing
capacities, by applying the US Aviation Certification SAE AIR 1316
specification to our Drawbar Pull (DBP) calculations, and the method we
use to test the DBP capacities.
We calculate the true DBP capacity of our aircraft tractors and make sure
the towing capacity we market for our tractors is true in all weather
conditions, for all plausible surface grades, and for all potential weights of
aircraft our tractor may move.
The Eagle Tugs’ testing protocol requires a gradual and consistent
application of power, while recording DBP, until wheel slip or torque
converter stall is achieved, indicating maximum DBP on that surface.
13. Drawbar Pull (DBP) and Proper Testing
14. Drawbar Pull (DBP) and Proper Testing
DBP testing shall be smoothly accelerated without jumping and/or jerking
15. Aircraft Tractor Design
Torque conversion and gear ratio to move expensive aircraft smoothly and safely.
All Wheel Drive and Unibody welded chassis creating an extremely smooth push back
in all conditions and environments.
AWD TT & USATS aircraft tractor (NSN 1740 01 461 4279).
1. 3 Year /3,000 Hour Warranty
2. YANMAR Diesel Engine
3. All Wheel Drive for controlled smooth pushback in all weather conditions
4. Low-profile design under 47” for maximum visibility and safety
5. Ergonomic and safe “slide in and out seating”
6. Intuitive Automotive Controls (Mil standard 1472 human engineering)
7. Average unit produced in less than 4 weeks
8. Standardized parts and tires for PM and replacement
9. Custom color and graphics (your corporate logo & colors) available
On Reliability, First Sergeant JT Lee, 160 th SOAR:
“Right now we’re getting around 2,500 hours between failures and I think the only thing we’ve had to
do on it besides oil changes and changing filters is to replace a steering hydraulic pump. They could
probably last forever.”
16. Baggage type tractors used in this weight class..
Lacking All Wheel Drive
Non ergonomic operators
Reduced visibility due to
Reduced front end control
No direct line of sight to
Eagle Aircraft Tractor Design
Example of low profile design and direct
hitch view of the Eagle AWD TT-series
17. Aircraft Tractor Design
NSN 1740 01 461 4279
18. Over 20 years of in-theater operations.
NSN 1740 01 461 4279
19. Operating in the following partial* list of organizations:
Alaska Air National Guard
Brazilian Air Force
Canadian Defense Forces
US Air Force
US Coast Guard
Kennedy Space Center
Michigan Army Natl. Guard
Romania Army Land Forces
Royal Saudi Air Force
Taiwan National Police
Turkish Air Force
US Marshals Service
U.A.E. Air Force
*Eagle supplies many classified organizations as well
20. Aircraft Tractor Design Matrix
Eagle AWD Aircraft Standard (Baggage) The Eagle Aircraft Tractor
Tractors Tractor Advantage
Not required, too AWD provides controlled
Only AWD tractors in
All Wheel Drive 4,000-12,000 lb DBP
expensive for pulling traction on all surfaces/Lighter
Better for maneuvering around
Low Profile Only 38-48 in. tall 55-60 in. or taller aircraft. Less chance for
accidental damage to aircraft
Mid-operator, w/ low profile
Slide in and out, ergo Climb up and down, strain
Ergonomics design on operator
design, allows for easy
No front hitch vision, must Direct operator visibility for
Visibility hitch/nose wheel vision
use mirrors safer, more efficient operation
through sight tunnels
Same size front and Large rear and small front Same size tires/Equal weight
Tire Size/Steering rear tires with equal tires, often too light in the distribution allow for controlled
weight distribution front end steering when moving aircraft
Proprietary power train
Cost competitive market,
Properly selected power component relationship results
Reliability train relationships
must use lower cost
in smooth operation and
21. Aircraft Tractor Design
Aircraft tractor design versus standard (baggage) tractor design conclusions:
• Standard (baggage) tractors are intended to pull carts, not multi-million dollar
aircraft. These are clearly two different operations with separate sets of
• Standard (baggage) tractors compete in a very price competitive market, in which
manufacturers have to control costs in order to compete. This formula does not
work when you try to apply it to moving aircraft, in all weather conditions, day in
and day out. Lower cost tractors, when used at their maximum capacity for
prolonged use, are much less reliable.
• Aircraft tractors, designed specifically to move aircraft, with towing capacities
directly matched with the weight of the aircraft, are much more efficient, safe and
reliable. Providing lower through-life costs.
• Not only do the features of AWD aircraft tractors provide operators the proper
equipment to safely and efficiently accomplish their jobs, the added reliability
alone makes Eagle AWD aircraft tractors the right choice for moving
22. Utility Standard Aircraft Tractor Design
Eagle Tugs was approached by members of the Army Special Forces out of Ft.
Campbell KY. The “160th” has been using the Eagle AWD TT-8 (8,000 lb. DBP)
aircraft tractors for several years. The 160th had a need for a utility aircraft tractor that
was AWD, that could move Army helicopters, but that could also carry up to a 2,000
lb. payload. The 160th chose Eagle Tugs because of the reliability of its aircraft
tractors, especially when deployed overseas in less than ideal operating environments
under mission critical conditions.
Based on the needs described by the 160th, Eagle designed a utility aircraft tractor
with the same reliable AWD power train as the TT-series. The new design is named
USATS, for Utility Standard Aircraft Towing System.
• AWD – The only AWD aircraft tractor in its weight class
• Flexible – 6,000 lb. DBP unloaded, up to an 8,000 lb. DBP loaded
• Utility – Can carry up to a 2,000 lb. payload on a 60” X 90” deck
• Ergonomic Operation – Slide in and out design. No climbing.
• Reliable – The only tow tractor in the industry with a 3-year/3,000 hr warranty
24. Presented by:
Justin Akinleye - Director of International Sale
Manufactured in the State of Michigan:
26111 Northline Rd
Taylor, MI 48180
Global Sales Office:
Franke Care System
Throughout the world.