WO2010116383A2

WO2010116383A2 - An undercarriage that combines the advantages of caterpillar tracks (ct) and tyres

Info

Publication number: WO2010116383A2
Application number: PCT/IN2010/000197
Authority: WO
Inventors: Mittu Neethala
Original assignee: Mittu Neethala
Priority date: 2009-04-08
Filing date: 2010-03-29
Publication date: 2010-10-14
Also published as: WO2010116383A9; WO2010116383A3

Abstract

An undercarriage (40) which combines both tracks (9) and tyres (14) is provided. During the landing roll phase, only the tracks (9) take the brunt of the impact, and the flaps (42, 42a) incorporated at a convenient spot near the mouth of the undercarriage well (12) are lowered to increase the drag for the aircraft. During the take-off phase, the flaps (42, 42a) are retracted, and the aircraft initially run on tracks (9) till it attains an optimum speed of the undercarriage (40) with tracks (9), once a sustainable lift is created the tyres (14) are then deployed to take off.

Description

1. TITLE OF INVENTION: An undercarriage that combines the advantages of caterpillar tracks (CT) and tyres.

3. The following specifications describe this invention. 4. DESCRIPTION

This im ention relates to an improved undercarriage (IU) that is equipped with BOTH caterpillar tracks and tyres for use, more particularly _y in the aero industries.

THE NEED FOR THIS CONCEPT

Aviation is represented by three factors (1) weather (2) aircraft and (3) human factors. While the latter twα factors are under control to a large extent there is no understanding of weather which plays a vital role to ensure safety of the aircraft during the landing roll phase. Now, by improving the* technology of the landing gear it is possible to raise the bar on safety and minimize the risks involved in this phase. Further, it is now possible to make air travel more safe, reliable and cost effective (by reducing the operational and maintenance costs).

In prior art aircraft are equipped with a landing gear, called a bogie, comprising of several multiaxle wheels having tyres that are deployed on both occasions, while taking off and landing.

Now, for the advantages of using tyres :

1. Less rolling resistance and drag when compared to caterpillar tracks.

2. Serves as a good cushion against hard landing impacts.

The disadvantages being:

1. A burst tyre due to impact of landing can cause the aircraft to veer off — course with, possible, catastrophic consequences.

2. A bald tyre is dangerous, especially, in wet conditions. r

3. Less contact area with the runway resulting in more fiction, wear and tear.

As such these expensive tyres have a short life span. 4. The wear & tear is caused by hard landing, a descent of 600 feet per minute which is the maximum rate of descent permitted. This proves too expensive when the condition of the tyre is dependent on the skill of the pilot. Besides, there are structural limits on the landing gear.

5. Emergency braking during the take off stage and landing roll phase can also cause the tyre to catch fire, burst and veer off - course, with disastrous consequences.

6. Air craft tyres are filled with pressurized water to withstand over 1000 lbs/ sq. inch pressure i.e. 5 times safety factor. This adds to the manufacturing cost of the tyre and weight of the under carriage enormously.

7. Good condition of tyre is important for traction.

8. Air craft tyres are built to conform to high standards of excellence and are a single integral whole. As such even a miniscule percentage of damage can render the whole expensive tyre useless.

9. Increased maintenance costs for maintaining the right tyre pressure as this aspect is one of the factors that determine good tyre condition.

10. Maintenance crews have to be skilled and alert as any lapse (over inflation) on their apart can cause the tyre to burst with fatal consequences.

11. aircraft tyres being custom built, its regular replacements, adds to high operational costs as wear & tear of tyre is most during the landing roll phase.

12. Now, an aircraft using tyres for its undercarriage covers the distance of 175 feet / sec after landing. Statistics covering 3 years (2005 - 2007) reveal that maximum runway accidents are caused by (a) landed long (b) landed long and fast (c) landed long and tail wind (d) late thrust reverser deployment (e) unstable and oscillating approach and (f) floated on wet runway. 13. Severe landing impact can cause the axle to distort & tyre to burst with dangerous consequences.

These adverse conditions can happen due to: a. Pilot fatigue or a phenomenon called "micro sleep". Two to ten seconds micro sleep events have known to occur for all human beings and it can occur when one is wide awake too! For pilots, when this occurs during the flare and landing roll phase of the flight, in adverse weather, it can mean the difference between safe landing and a fatal crash.

b. 11 to 12.8 seconds delay, while landing in rain, in selecting the reverse thrust or a runway with suspected friction characteristics can cause an accident resulting in post accident fire.

c. Communication error of Air Traffic Controller (ATC) is NOT rare.

d. Rain conditions accompanied by changing winds, especially tail winds, becomes a dangerous recipe. Aircraft tend to over shoot the runway while landing in rain. Further, aircraft which require 3000 feet of runway to stop in dry conditions will require 6000 feet of runway when it is wet. When conditions are declared contaminated -or slippery the distance required for landing is moτe.l

e. Periods of heavy rain when day becomes night! This aspect becomes more challenging for the pilot.

f. Runway excursions - when aircraft over run the runway or veer off the side of the runway. g. Reduced runway friction and improper maintenance of runway i.e. not clearing rubber debris.

h. All aircrafts have structural limit for their landing gear. The maximum rate of descent is 600 feet per minute. A glide slope of up to 3.25° will ensure a controlled flare and landing within the limit. Any higher angle will require a descent rate of 800 to 900 feet / minute. A positive flare in the correct time is required. Any delay can result in a hard landing or a late touch down. These are major threats while landing in heavy rain conditions.

From the foregoing it is clear that all adverse conditions that can cause a disaster is measured in terms of delay in "seconds and microseconds", one way of obviating these problems would be is to incorporate measures / means that would enable the pilot to have more reaction time (in terms of seconds)^when time is the most demanding aspec^inspite of his skill. In aviation, accidents may be a product of human error, either due to active or latent failure.

Active failures are those due to pilot error while a latent failure is that which lies dormant due to systemic failure but which rears its head at a later stage. Whether active or latent to avoid failures extra time made available (in seconds) is vital.

DEMERITS OF TRACKS:

This aspect has been considered, to the extent of material available, and analyzed by the inventor. Now. the column linking the fuselage to the under carriage has to be strengthened to reduce structural stress caused by restraining the inertia of the aircraft using the improved undercarriage. This could add to the weight factor. However, the structural stress may be minimized by incorporating linear acting buffers 34 (see fig 2e) that cushion the energy of the linear movement during the landing roll phase, while braking, accelerating and during take off phase.

Considering the various beneficial factors ( 1) pertaining to enormous increase in safety (prime consideration in aviation), (2) reduced operational and maintenance cost (aircraft and airstrip), (3) greater stability and reliability in adverse conditions, (4) reduced tyre weight (as it is now pneumatic). any demerits of using the undercarriage comprising of tracks and tyres Λyόuld'beigjreatly offset by the aforesaid advantages.

More particularly the following pictures will give a better understanding of the proposed invention:

Photo : A Comparative analysis TRACKS Vs TYRES

1. For the same vehicle length the tracks provide much greater contact area with the tarmac.

2. Better grip. therefore better braking efficiency.

3. Inherent drag & rolling resistance of this undercarriage, comprising of tracks and tyres, as such the aircraft needs a shorter runway during the landing roH phase - added safety.

4. Have greater stability and resistance to roll over even while working on an incline as such much added safety in the landing roll phase.

5. The steel tracks offer more resistance to flexing and prevent roll over; as opposed to tyres, in the landing roll phase.

6. Less maintenance costs when compared to tyres and therefore less operational costs for the airlines.

7. With steel tracks the landing impact is distributed over a larger area.-al^'such damage to tyres, burst tyres and axle distortion, which is normal in the case of undercarriage with tyres, is obviated.

8. Tracks offer unsurpassed stability, in gusty tail wind conditions, in the landing roll phase.

WHEELED EXCAVATORS (WE)

Photo : B

Photo : C

1. As seen in photo B the wheeled excavator (WE) will be stable only when it is loaded in the longitudinal axis and can perform only to a limited degree of incline after which, the tyres will flex causing the excavator to topple over.

2. See photo C here the wheeled excavator is provided with a rotating boom,

To improve stability, as such it is provided with hydraulically operated stabilizing feet. Needles to say the use of such an excavator with tyres is very limited and the same is not versatile and user friendly as in the case of excavator's with tracks.

Photo : D

PHOTO D SHOWS A TRACKED PILE DRIVING MACHINE

WHICH ENDORSES THE STABILITY OF TRACKS IN

ADVERSE OPERATING CONDITIONS

The first object of this invention is to provide the aircraft with an undercarriage : a. that on landing provides greater rolling resistance and drag there by making available (even to an unskilled pilot) the extra seconds so necessary to obviate the disastrous consequences of active and latent failures and when the flaps (42 & 42a) are deployed the drag is even more as shown in figures 2 & 2d. b. that permits the same to land safely in oscillating & tail wind conditions. c. that has better braking efficiency d. that performs safely in wet and slippery runway conditions e. that deploys the tyres, while the tracks retract, to enable the aircraft to take off with as much ease as is afforded by the existing landing gear comprising of ONLY tyres.

Another object of this invention is to prevent the aircraft from roiling over under adverse weather conditions in the landing roll phase.

Yet another object of this invention is to reduce operational and maintenance cost of the expensive and specially formulated tyres and enable the aircraft to land safely in improperly maintained airstrips.

The first object of this invention is achieved by providing the undercarriage with the improved caterpillar track (CT) which because of its inherent rolling resistance and drag enables the aircraft to come to a halt, with runway to spare, as most accidents are caused by a condition termed "landed long and fast". Yet enable the aircraft to take off with as much ease as in existing undercarriage- Further advantages being :

1. because of the width of the caterpillar track it provides greater contact area with reduced ground pressure. This way wear and tear on the solid rubber clad track / segments is reduced. However, if required by the pilot (to increase braking efficiency), the spoilers can be deployed.

2. CT's perform well in oscillating conditions and stabilize the aircraft on landing and also prevent the same from a roll as the metal backed rubber segments offer better mechanical strength and resistance. 3. CT's are structuraHy stronger, reliable and more durable than undercarriages provided with ONLY tyres.

4. Due to greater contact area with the runway they provide better traction and better braking efficiency.

5. With solid rubber clad track the possibility of tyre burst, while landing and during emergency braking, is obviated. Thus the possibility of consequential veering off the runway is also eliminated. Further being provided with a thick solid rubber lining with "sipes" (that prevent aquaplaning) and with a rubber clad track being directly supported by the steel links of the caterpillar track the disastrous consequences of landing in wet and oscillating conditions will be greatly reduced. Even if the rubber lining burns_<the steel links of the CT will still support the whole aero plane safely.

6. Even if the aircraft veers off course, on landing, the same can be brought back on to the airstrip with better control and less damage.

7. Bald condition of the lining / segment will not pose any problem in wet conditions.

8. Reduced maintenance and inspection procedures when compared to undercarriages equipped with only tyres.

9. Less replacement cost (as, here, tyres are deployed ONLY during take off) and only that segment / lining need be replaced that has reached its limit of serviceability. lft. Due to greater contact area with the runway they perform well in wet conditions with tail wind and provide greater stability.

The second object of this invention is achieved by the improved under carriage which has a rubber lining backed by a rigid streel track. Now this offers more mechanical resistance to a roll as opposed to an under carriage with ONLY tyres that, being flexible, are vulnerable to a roll. The third object of this invention is achieved by lining the endless steel track of the improved undercarriage, with rubber cladding that has proved its reliability, efficacy and durability for over hundred years in armored battle tanks. It may be noted that conditions of an airstrip are far better than the rugged, undulating and marshy terrain on which armored battle tanks operate. Further, as caterpillar track s are deployed ONLY while landing (a) the rubber clad steel tracks (b) the rubberized road wheels (that support the steel track) (c) the suspension system and (d) the energy absorbing buffers of the column (connecting the improved under carriage with the fuselage) will offer better cushioning and resilience than what¹ the existing pneumatic / water filled tyres normally would. Thereby rendering this concept, technically & commercially viable option as opposed to an undercarriage equipped with ONLY tyres.

It may be added that to increase drag, in the landing roll phase, a flap 42 as seen in figures 2 and 2d may be incorporated at a convenient spot near the mouth of the undercarriage well 12. The flap 42 and 42a can be retracted to firmly rest in its housing during the take off stage as seen in figure 2a. However, after completion of the take off stage, and with the undercarriage fully retracted, (see fig 2d) the flaps 42 and 42a can be made to swivel back to act as a cover for the undercarriage well 12.

During the "en-route" phase of the flight the flap 42 / flaps 42 & 42a (depending on the requirement of the pilot) can ALSO be deployed to counter air turbulence & other emergencies to help control and stabilize the aircraft to ensure its safety.

Now, for the description of this invention with reference "to the accompanying drawings: Fig 1 shows the side view of the aircraft with a bogie comprising of multiaxle wheels and nose wheel.

Fig 2 shows that side view of the aircraft fitted with an improved undercarriage (IU) comprising of caterpillar tracks that are deployed while landing only. The flap 42 is lowered to increase the drag.

Fig 2a shows the side view of the same aircraft when tyres from the IU are deployed while taking off. The flap 42 here is retracted to enable the aircraft to roll smoothly during the take offstage.

Fig 2b shows the front view of the wide body jet incorporating an IU comprising of caterpillar tracks and tyres.

Fig 2c shows the front view of the same wide body jet where, for the purpose of clarity, a configuration of IU comprising of twin caterpillar tracks and tyres are shown with the suspension system comprising of buffers Λ

Fig 2d shows the aircraft 32 with flaps 42 and 42a in a deployed condition.

Fig 2e shows the linear stress of the aircraft being cushioned by buffers 34.

Now for detailed description of the improved undercarriage (IU) with the reference to the accompanying drawings. Fig 1 shows the side view of an aircraft 32 fitted with a bogie 8 having multiple tyres 14. The bogie 8 is housed irr a wheel well 7 (during flight) and is deployed by activating the deployment mechanism 30 and sliding hydraulic ram 15 which lower the bogie 8 prior to landing. In prior art the bogie 8 has ONLY tyres that are deployed, BOTH during landing and take off.

Fig 2: here, the aircraft 32 is equipped with an improved undercarriage IU 40 comprising of both rubber clad tracks 9 and wheels 14 (see fig 2a). While in flight the IU 40 is housed in an undercarriage well 12. The improved undercarriage 40 is deployed by activating the mechanism 15 & 30. On landing the rubber clad, metal tracks 9 take the brunt of the impact while the idlers 10 add to the rigidity of the rubber clad tracks 9 while landing in oscillating conditions. The flap 42 is deployed to increase the drag.

Fig 2a shows the wheels 14 deployed during take off while the rubber clad metal tracks 9 are retracted, the flap 42 is retracted to enable the aircraft to take off smoothly with minimum drag. However, after the undercarriage is fully retracted into its well^ the flap 42 can be swiveled back to act as a cover for the undercarriage well 12.

Fig 2b shows the front view of the wide body jet equipped with improved undercarriage 40 comprising of rubber clad metal tracks 9 and tyres 14. The flap 42 is not shown for clarity puposes.

Fig 2c shows a more detailed sketch of the improved undercarriage 40 comprising of rubber clad tracks 9 and tyres 14. Here, a provision is made to simulate the cushioning effect that is provided, normally by aircraft that land on tyres but without any adverse effects. Here, the sliding hydraulic ram 15 is provided with an extension that serves as buffer seats 21 for the buffers 25 that rest on the fixed base 37 provided by the UC 40. On landing _;the buffers 25 compress to cushion the energy of the impact. Thereby providing more resilience then what tyres would. The flap 42 is not shown for clarity purposes.

Fig 2d shows the flaps 42 & 42a deployed while the aircraft is in the landing roll phase.

Fig 2e shows the hydraulic ram 15 sliding in the linear guide way 36. The linear stress caused by the aircraft 32 is cushioned by buffers 34.

OPERATION

During the take off phase the aircraft can initially run on tracks till it attains the optimum speed of an UC with tracks. Once a sustainable lift is created the wheels are then deployed to take over. This way the number of tyres required can be reduced with accruing benefits & advantages.

While I have explained in detail my afore said invention of an improved undercarriage equipped with both caterpillar tracks and tyres I do not wish to limit myself to the exact form shown, described and illustrated. The configuration of 1) the caterpillar tracks and tyres and their numbers and 2) the extra cushioning (if required) to compensate for the cushioning and resilience that is provided by undercarriage equipped with tyres, during both phases of landing and take off, can be varied based on the extensive R & D work in this area. It is to be expressly understood that this invention is susceptible to such changes and modifications which shall define no material departure from the salient features of this invention herein described and illustrated.

Claims

1 claim:

1 ) an undercarriage 40 characterized in that it combines the advantages of tracks 9 and tyres 14 to form a single integral whole; (2) an undercarriage 40 as claimed in claim 1 where the tracks 9 and tyres 14 can be jointly or independently deployed ; (3) an undercarriage 40 as claimed in claims 1 and

2 where the configuration of tracks 9 and tyres 14 and their numbers can be varied to suit specific requirements of the concerned industries; (4) an aircraft 32 as claimed in the preceeding claims that has flaps 42 & 42a (5) an undercarriage 40 as claimed in any of the aforesaid claims where the energy of the linear movement of the aircraft 32 (on the ground) is cushioned effectively by the buffers 34 and (6) an undercarriage 40 as claimed in any of the aforesaid claims and substantially herein before described and illustrated with reference to the accompanying drawings contained in three pages.