Anti-shock body
A streamlined pod reducing wave drag at transonic speeds.
An anti-shock body is a streamlined pod placed on top of a wing to cut down on wave drag during transonic flight—roughly Mach 0.8 to 1.0, the typical cruising speed of most jet airliners. It is also called a Whitcomb body, Küchemann carrot, or speed bump, and it helps apply the area rule.
The anti-shock body was one of several methods for putting the then-new area rule into practice. Another method was reshaping the fuselage.
The concept was worked out independently in the early 1950s by two aerodynamicists: Richard Whitcomb at NASA and Dietrich Küchemann at the British Royal Aircraft Establishment. The body is closely tied to the area rule, a recent innovation that minimizes wave drag by ensuring the aircraft’s cross-sectional area changes smoothly along its length. The part of the body extending past the wing’s trailing edge was considered less important than the part on the wing surface itself, which slowed supersonic airflow to produce a weaker shock and acted as a fence to stop outward flow. That extension was only long enough to prevent flow separation. Whitcomb noted that once the supercritical airfoil was introduced, the anti-shock body was no longer needed on the wing’s top surface, because both approaches reduced or eliminated the shock and its associated drag.
Aircraft that have used anti-shock bodies include the Convair 990 and Fokker 100 airliners. Küchemann carrots were added to the Handley Page Victor to provide space for carrying chaff. They did not improve the aircraft’s performance, and when they were no longer needed for that purpose, they were left in place to avoid the cost of removal. Several Tupolev aircraft from the Soviet Union used Küchemann carrots as gear storage pods, mounted mid-wing and extending past the trailing edge—examples include the Tu-104, Tu-134, and Tu-154 airliners, as well as the Tu-16 and Tu-95 bombers. Boeing tested similar bodies on a wind tunnel model of the 707. While the speed at which drag suddenly increased was raised, the extra friction drag from the bodies’ surface area canceled out any benefit.
Modern jet aircraft instead use supercritical airfoils to minimize drag from shockwaves on the upper surface.
- Speed range
- Mach 0.8–1.0
- Also known as
- Whitcomb body, Küchemann carrot, speed bump
- Developers
- Richard Whitcomb (NASA), Dietrich Küchemann (British Royal Aircraft Establishment)
- Development period
- early 1950s
- Example aircraft
- Convair 990, Fokker 100, Handley Page Victor, Tu-104, Tu-134, Tu-154, Tu-16, Tu-95
Lore & Background
The theory behind the anti-shock body was independently developed during the early 1950s, by two aerodynamists, Richard Whitcomb at NASA and Dietrich Küchemann at the British Royal Aircraft Establishment. The anti-shock body is closely associated with the area rule, a recent innovation of the era to minimise wave drag by having a cross-sectional area which changes smoothly along the length of the aircraft. The extension beyond the trailing edge was considered secondary to the body on the wing surface, which slowed the supersonic flow to give a weaker shock and acted as a fence to prevent outward flow. The extension was only long enough to prevent flow separation.
Aircraft that have used anti-shock bodies are the Convair 990 and Fokker 100 airliners. Küchemann carrots were added to the Handley Page Victor to provide volume for carrying chaff. They did not improve the performance of the aircraft, and when they became redundant for their intended purpose they were left in place to save the cost of removing them. Several Tupolev aircraft of the Soviet Union utilized Küchemann carrots as gear storage pods, which were mounted mid-wing and extended past the trailing surface. Examples are the Tu-104, Tu-134 and Tu-154 airliners and the Tu-16 and Tu-95 bombers.
Boeing tested the effect of adding similar bodies to a wind tunnel model of the Boeing 707. Although the speed beyond which the drag rose abruptly was increased, the additional friction drag on the surface area of the bodies cancelled out any advantage.
Reader's Guide
The anti-shock body was one of a number of ways of implementing what was then the recently developed area rule, with another being fuselage shaping. Its significance lies in reducing wave drag at transonic speeds, which includes the typical cruising range of conventional jet airliners. Whitcomb stated that the anti-shock body was no longer required on the top surface of a wing when the supercritical airfoil was introduced because they both decreased the strength of, or eliminated, the shock and its attendant drag. Modern jet aircraft use supercritical airfoils to minimize drag from shockwaves on the upper surface, marking the legacy of the anti-shock body as a transitional solution that was superseded by airfoil design advances. The article notes that the anti-shock body did not always improve performance, as seen on the Handley Page Victor where it was added for chaff storage, and on the Boeing 707 where friction drag cancelled any advantage.
Did You Know?
- It was independently developed in the early 1950s by Richard Whitcomb and Dietrich Küchemann.
- Küchemann carrots on the Handley Page Victor were used to carry chaff and did not improve aircraft performance.
- Boeing tested anti-shock bodies on a wind tunnel model of the 707, but added friction drag cancelled any advantage.
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