Excerpt

Excerpt from The Aeroplane Speaks, by H. Barber

FUNCTION OF INTERPLANE STRUTS.--These struts have to keep the lifting
surfaces or “planes” apart, but this is only part of their work. They
must keep the planes apart, so that the latter are in their correct
attitude. That is only so when the spars of the bottom plane are
parallel with those of the top plane. Also, the chord of the top plane
must be parallel with the chord of the bottom plane. If that is not so,
then one plane will not have the same angle of incidence as the other
one. At first sight one might think that all that is necessary is to cut
all the struts to be the same length, but that is not the case.

Sometimes, as illustrated above, the rear spar is not so thick as the
main spar, and it is then necessary to make up for that difference by
making the rear struts correspondingly longer. If that is not done, then
the top and bottom chords will not be parallel, and the top and bottom
planes will have different angles of incidence. Also, the sockets or
fittings, or even the spars upon which they are placed, sometimes
vary in thickness owing to faulty manufacture. This must be offset by
altering the length of the struts. The best way to proceed is to measure
the distance between the top and bottom spars by the side of each strut,
and if that distance, or “gap” as it is called, is not as stated in the
aeroplane's specifications, then make it correct by changing the length
of the strut. This applies to both front and rear interplane struts.
When measuring the gap, always be careful to measure from the centre
of the spar, as it may be set at an angle, and the rear of it may be
considerably lower than its front.

BORING HOLES IN WOOD.--It should be a strict rule that no spar be used
which has an unnecessary hole in it. Before boring a hole, its position
should be confirmed by whoever is in charge of the workshop. A bolt-hole
should be of a size to enable the bolt to be pushed in, or, at any rate,
not more than gently tapped in. Bolts should not be hammered in, as that
may split the spar. On the other hand, a bolt should not be slack in its
hole, as, in such a case, it may work sideways and split the spar, not
to speak of throwing out of adjustment the wires leading from the lug or
socket under the bolt-head.

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Explanation

Detailed Explanation of The Aeroplane Speaks (Excerpt by H. Barber)

Context & Source

The Aeroplane Speaks (1917) by H. Barber is a technical manual written during the early days of aviation, a period when aircraft design and construction were still evolving rapidly. The book was likely intended for mechanics, engineers, and pilots involved in the assembly and maintenance of biplanes—aircraft with two sets of wings (top and bottom) connected by struts and wires.

At the time, aviation was transitioning from wood-and-fabric constructions to more standardized metal designs, but many aircraft still relied on wooden spars, wires, and interplane struts for structural integrity. Barber’s work reflects the practical, hands-on knowledge required to ensure an aircraft was airworthy, emphasizing precision in construction to prevent catastrophic failures.

This excerpt focuses on two key aspects of biplane construction:

1. The function and adjustment of interplane struts (which maintain wing alignment).
2. Proper techniques for boring holes in wooden spars (to avoid structural weaknesses).

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Themes & Key Ideas in the Excerpt

1. Precision in Aircraft Construction

The excerpt underscores the critical importance of exact measurements and adjustments in aviation. Unlike modern mass-produced aircraft, early biplanes were often hand-built, meaning small errors in construction could lead to asymmetrical lift, instability, or structural failure.

• "The struts must keep the planes apart, so that the latter are in their correct attitude."

  • The alignment of the top and bottom wings (planes) is essential for equal lift distribution.
  • If the chords (the imaginary straight line from the leading to the trailing edge of the wing) are not parallel, one wing will generate more lift than the other, causing the aircraft to roll or yaw uncontrollably.

• "At first sight one might think that all that is necessary is to cut all the struts to be the same length, but that is not the case."

  • This highlights the misconception that uniformity alone ensures safety.
  • In reality, manufacturing imperfections (e.g., uneven spar thickness, misaligned fittings) require custom adjustments to each strut.

2. Compensating for Human and Manufacturing Errors

Early aviation relied heavily on craftsmanship, meaning human error and material inconsistencies were common. Barber’s instructions account for these variables:

• "The rear spar is not so thick as the main spar, and it is then necessary to make up for that difference by making the rear struts correspondingly longer."

  • If the rear struts are too short, the trailing edge of the wing will droop, altering the angle of incidence (the angle at which the wing meets oncoming air).
  • This would cause one wing to stall before the other, leading to a loss of control.

• "The sockets or fittings... sometimes vary in thickness owing to faulty manufacture."

  • Even small deviations in metal fittings could throw off wing alignment.
  • The solution? Measure each gap individually and adjust strut lengths accordingly.

• "Always be careful to measure from the centre of the spar, as it may be set at an angle."

  • A misaligned measurement (e.g., measuring from the top instead of the center) could lead to incorrect strut lengths, destabilizing the aircraft.

3. Structural Integrity & the Dangers of Improper Modifications

The second part of the excerpt warns against unnecessary or poorly executed modifications to wooden spars (the main structural beams of the wings):

• "No spar be used which has an unnecessary hole in it."

  • Every hole weakens the wood, increasing the risk of cracking under stress.
  • This was especially dangerous in combat aircraft, where G-forces and vibrations could exacerbate structural flaws.

• "A bolt-hole should be of a size to enable the bolt to be pushed in, or at any rate, not more than gently tapped in."

  • Too tight a fit → risk of splitting the wood when hammered.
  • Too loose a fit → bolt wobbles, wears down the hole, and may eventually tear through the spar.

• "A bolt should not be slack in its hole, as... it may work sideways and split the spar."

  • Loose bolts could shear under load, leading to wing collapse mid-flight.

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Literary & Stylistic Devices

While The Aeroplane Speaks is a technical manual, Barber employs several rhetorical and stylistic techniques to ensure clarity and urgency:

1. Direct Address & Imperative Mood

   • "Always be careful to measure from the centre of the spar."
   • "No spar be used which has an unnecessary hole in it."
   • The command-like structure reinforces the life-or-death stakes of following instructions precisely.

2. Cause-and-Effect Reasoning

   • Barber explains consequences to justify his instructions:
     • "If that is not done, then the top and bottom chords will not be parallel..." → leads to unequal lift.
     • "Bolts should not be hammered in, as that may split the spar." → structural failure.

3. Repetition for Emphasis

   • "The struts must keep the planes apart" (repeated with variations).
   • Reinforces the primary function of struts before delving into adjustments.

4. Anticipating Misconceptions

   • "At first sight one might think that all that is necessary is to cut all the struts to be the same length, but that is not the case."
   • Barber preempts common mistakes, making the manual more practical.

5. Technical Jargon with Clarifying Definitions

   • "Chord" (defined implicitly as the line between leading and trailing edges).
   • "Angle of incidence" (explained through context—how wings meet airflow).
   • "Gap" (the measured distance between spars).
   • This balances precision with accessibility for mechanics who may not be engineers.

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Significance of the Excerpt

1. Historical Context: Early Aviation’s Trial-and-Error Era

• Before standardized manufacturing, aircraft were hand-built, meaning each one was slightly different.
• Barber’s manual reflects the practical wisdom gained from crashes, near-misses, and mechanical failures.
• His instructions were likely life-saving for pilots who depended on properly aligned wings and secure spars.

2. The Human Element in Engineering

• Unlike modern computer-designed, mass-produced aircraft, early planes required constant adjustments by skilled mechanics.
• The excerpt shows how small errors (a misaligned strut, a poorly drilled hole) could have fatal consequences.

3. The Transition from Craftsmanship to Standardization

• Barber’s work bridges the gap between artisanal aircraft building and the emerging need for precision engineering.
• His emphasis on measurement, adjustment, and quality control foreshadows the industrial standardization that would dominate later aviation.

4. Relevance to Modern Engineering Principles

• While materials and methods have changed, the core principles remain:
  • Alignment matters (e.g., in modern composite wings).
  • Structural integrity depends on precise tolerances.
  • Human error must be accounted for in design.

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Conclusion: Why This Excerpt Matters

This passage from The Aeroplane Speaks is more than just a technical guide—it’s a window into the fragile, high-stakes world of early aviation. Barber’s methodical, no-nonsense instructions reveal:

• The delicate balance required to keep an aircraft airborne.
• The human skill and attention to detail that defined early flight.
• The evolution from handcrafted machines to the precision-engineered aircraft of today.

For modern readers, it serves as a reminder that even small details can mean the difference between flight and disaster—a lesson as relevant in 1917 as it is in 2024.