When is an antitear strip required?

on an aircraft with a VNE of over 250 mph
on an antique aircraft
on a wood spar

Question

When is an antitear strip required?

on an aircraft with a VNE of over 250 mph
on an antique aircraft
on a wood spar

BlackTom AI · Accepted Answer

Antitear strips are required on fabric-covered aircraft that have a VNE (never-exceed speed) greater than 250 mph because higher aerodynamic loads greatly increase the risk that a small tear in the fabric will propagate rapidly.

1) Relevant knowledge points and concepts
- VNE is the maximum permissible speed; aerodynamic loads scale with the square of velocity (dynamic pressure q = 1/2 ρ V^2).  
- Fabric coverings can develop a small rip; an antitear strip (a reinforcing tape or material sewn or bonded over seams) spreads the load and arrests tear propagation.  
- Regulatory practice sets a practical threshold of 250 mph for requiring additional reinforcement on fabric surfaces.

2) Step-by-step reasoning
- As speed increases, the dynamic pressure on surfaces increases with V^2, so the tearing force on fabric increases rapidly.  
- At speeds above 250 mph, the probability and severity of tear propagation becomes high enough that a preventive structural feature (antitear strip) is required.

3) Calculations (illustrating the physics)
- Convert 250 mph to SI: 250 mph × 0.44704 = 111.76 m/s.  
- Dynamic pressure at sea level: q = 0.5 × 1.225 kg/m³ × (111.76 m/s)² ≈ 0.6125 × 12,493 ≈ 7,650 N/m².  
- For comparison, at 200 mph (89.41 m/s), q ≈ 0.6125 × 7,994 ≈ 4,896 N/m².  
- The dynamic pressure at 250 mph is about 56% higher than at 200 mph, showing why additional reinforcement is justified.

4) Why the correct answer is correct
- The requirement is specifically tied to the VNE threshold (over 250 mph) because of the rapid increase in aerodynamic loading and the risk of catastrophic fabric failure; antitear strips mitigate that risk.

5) Why the other options are incorrect
- “On an antique aircraft”: age or classification (antique) does not automatically mandate antitear strips; the requirement is based on speed and fabric exposure, not simply being antique.  
- “On a wood spar”: an antitear strip addresses fabric tear, not the structural characteristics of a spar; wood spars are irrelevant to the specific fabric-tear prevention requirement.

Conclusion: Therefore, an antitear strip is required on an aircraft with a VNE of over 250 mph, which matches the provided answer.

When is an antitear strip required? on an aircraft with a VNE of over 250 mph on an antique aircraft on a wood spar单项选择题

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