Install Standard/Light Install Heavy
1. Question:
The system looks like a vast improvement over what is currently offered. Your engineering efforts addressing energy absorption during impact (the compression stroke) appear to be sound. One question though: What is the perceived effect during the expansion (return) stroke of the spring? I imagine it being rather firm…(bam?) and potentially hard on hardware & system longevity. What’s the track record so far - & what is the time-span of the record?
Answer:
We have been testing a prototype system on two CH-II student trainers for over two years (5/05) with hundreds of landings. They have seen several hard impacts that would have damaged the stock gear and undercarriage. Jackson Flight Center has this landing gear on all of their Challengers. The flight instructor has been in a couple of full compression landings. The first when the student did not flair at landing and the second was during an engine out off field landing. The aircraft and landing gear were not damaged.
The compressed gear will unload, but due to the progressive springs it will reduce the spring force as it travels back towards the stops. A dampener (urethane washer) has been installed between the stop washer and the spring support. This will help dampen the return impact.
2. Question:
On the trailing link type suspension, the pivot arm should not move backward past a max 45° down angle and the wheel displacement should be as close as possible and never forward to the steering axle.
Answer:
I agree with your statement that the pivot arm should not move back passed a 45° angle. It makes it difficult to steer the aircraft under full compression.
There are two sets of springs used to address that problem.
The primary blue or red springs are designed to work under normal landing conditions creating a smooth landing. The progressive force of the springs will help eliminate the jarring impact of hard landings. The blue or red spring starts at 0° (or the stock position) and moves to a 42° deflection angle during full compression of the primary springs. The pivot arm travels 3 inches with the lighter springs and will stop there, if the load is not excessive from a high impact landing.
The secondary heavy gold springs are designed to compress only under an extreme impact with the ground. The forward momentum of the aircraft will determine the direction that the aircraft will travel. The angle of the wheel will have less influence on the ability to steer the aircraft in the desired direction of travel during full impact. However, I believe the force absorbed by the TLS landing gear at full impact would have damaged the challenger’s stock landing gear, completely preventing any steering ability.
The deflection angle of the gold spring starts at 42° and moves to approximately 68° at full compression of the pivot arm. The pivot arm will travel over 6 inches at maximum force. During a hard landing impact the spring will only be in full compression for a brief moment, until the aircraft’s downward force and velocity are reduced.
3. Question:
How well will the Challenger taxi with your landing gear?
Answer:
The steering angle is inline with the airframe steering tube and the spring force will keep it from moving under normal taxing conditions (the wheel axle is inline with the steering tube as is the stock gear).
4. Question:
Will the suspension help smooth out the cracks in the taxiway or runway?
Answer:
The Trailing Link design has the pivot point 3 inches in front of the axle. This will allow the suspension to move freely without binding due to impact angles. A 90 degree impact straight on will not reduce or hinder movement. The best way to demonstrate this was by nailing a 4X4 post to the taxiway. (See video)
5. Question:
When completely compressed, the wheel moved from inline with the steering shaft to 5"-6" backward, this makes the steering caster design that could throw the plane outside of its travel if hitting a bump while turning.
Answer:
The force needed to compress the springs backward 6 inches is approximately 1,000 pounds. I do not know how an aircraft could exert that high of a load during a turn. If the aircraft was landing and hits a bump the pivot arm will move backward but the aircraft should not be turning at the speeds needed to completely compress the landing gear. The forward momentum of the aircraft has a greater influence on the direction of trail during a full compression impact.
6. Question:
The TLS is installed and has a higher ride height. You indicated most owners install the TLS with out modifying the ride height and students are flying in this configuration. I am concerned with only landing performance. So is there a landing performance difference?
Answer:
The trailing link suspension has a higher ride height due to the addition of the spring suspension system. The nose wheel and main gear wheel diameter (height) also have an influence on the ride height. A larger nose gear tire will give a slight nose up attitude and larger main gear tires will reduce it. This will not affect the performance of the aircraft and most of the owners install the TLS without modifying the ride height. Some owners use there aircraft on rough terrain and like the extra clearance.
The local flight instructor uses the non-modified height configuration on two of his student training Challengers and the ride height does not affect the ability to land. The wing's angle of attack is greater (higher) than the nose wheel during the flair and landing. The aircraft will remain on the ground as long as you are in within the normal landing speeds.
A modification can be made to the aluminum steering shaft length on the aircraft. The only requirement is that the spring bolts have clearance during full compression of 1.5 inches directly above and 1.5 inch behind the bolts in relation to the bottom of the nose cone. The aluminum steering shaft can be cut shorter. Slide the TLS on the aluminum steering tube and check the free space between the top of the TLS neck and the bearing support housing. Measure the distance and cut that off the end of the challenger stock aluminum steering shaft. Verify you have the 1.5 inch clearance for the bolt movement before cutting. This can be done in less than 30 minutes.
7. Question:
I use a nose wheel pant on my challenger, will it work with your nose gear?
Answer:
Our trailing link suspension is not designed to work with a nose wheel pant, because of the increased movement of the landing gear. The use of a nose wheel pant could cause a safety issue for yourself or damage to your plane.
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