Gravel kit
Aircraft modification to prevent FOD damage on unpaved surfaces.
A gravel kit is an aircraft modification that helps prevent foreign object debris (FOD) from causing damage or being ingested when operating on unpaved runways. These modifications typically involve measures to stop the nose gear from kicking FOD into the engines or against the underside of the fuselage and wings, as well as systems to keep each engine from sucking up debris directly from the ground ahead of it.
The most well-known example is the Boeing 737-200, which uses a gravel deflector—a wide, ski-like attachment on the nose wheel—along with vortex dissipators that blow compressor bleed air in front of each engine. This setup was long used by Alaska Airlines and remains in service with Air Inuit, Canadian North, Air North, and Nolinor Aviation in northern Canada. Some Boeing 727s also received gravel kits, but instead of a large nose-wheel deflector, they were fitted with smaller deflectors on all wheels to redirect FOD away from the rear-mounted engines. The McDonnell Douglas DC-9, MD-80, MD-90, and Boeing 717 series—all rear-engined aircraft—use similar deflectors on all landing gear to prevent FOD damage and ingestion. A gravel kit could also be installed on the BAe 146.
- Most notable application
- Boeing 737-200
- Airlines using the modification
- Alaska Airlines, Air Inuit, Canadian North, Air North, Nolinor Aviation
- Other aircraft fitted
- Boeing 727, McDonnell Douglas DC-9/MD-80/MD-90, Boeing 717, BAe 146
Lore & Background
The most notable application of this upgrade is the Boeing 737-200, which includes a gravel deflector mounted to the nose wheel, similar in appearance to a wide ski, and vortex dissipators using compressor bleed air in front of each engine. This modification was used by Alaska Airlines for many years and is still employed by Air Inuit, Canadian North, Air North, and Nolinor Aviation in northern Canada.
Some Boeing 727s were also fitted with specific gravel kits on the nose wheel, while the rest were fitted with devices in the form of smaller deflectors than those used on the 737, used on all wheels, to deflect FOD away so as to prevent the rear-mounted engines from ingesting FOD from a runway. Another rear-engined aircraft—the McDonnell Douglas DC-9/MD-80/MD-90 and Boeing 717 series—uses deflectors similar to those of the conventionally-equipped 727 on all their aircraft's landing gear to prevent FOD structural damage and ingestion. A gravel kit could also be fitted to BAe 146 aircraft.
Reader's Guide
The gravel kit's significance lies in enabling aircraft to operate safely on unpaved runways, a critical capability for airlines serving remote northern regions. The Boeing 737-200's kit, with its distinctive nose-wheel ski and vortex dissipators, became the most recognized example, used for many years by Alaska Airlines and still in service with several Canadian carriers. The adaptation of similar deflectors to other aircraft, including the Boeing 727, McDonnell Douglas DC-9/MD-80/MD-90, Boeing 717, and BAe 146, demonstrates the broader need for rough-field capability across different airframes. The legacy of the gravel kit is its role in extending aircraft utility to austere environments without paved runways, reducing FOD-related damage and engine ingestion risks through practical, field-proven modifications.
Did You Know?
- The Boeing 737-200 gravel kit includes a gravel deflector mounted to the nose wheel that resembles a wide ski.
- Vortex dissipators on the 737-200 use compressor bleed air in front of each engine.
- Some Boeing 727s were fitted with gravel kits on the nose wheel, while others used smaller deflectors on all wheels.
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