A mechanic is inspecting a dry-sump reciprocating engine oil system and needs to explain the primary advantage of this design compared to a wet-sump system to a trainee. What is the primary advantage?
- ADry-sump systems eliminate the need for an oil cooler entirely
- BDry-sump systems allow a larger external oil supply and better lubrication during extreme attitude maneuvers
- CDry-sump systems use significantly less oil than wet-sump systems overall
- DDry-sump systems do not require a scavenge pump since gravity returns all oil to the tank
Show answer & explanationAnswer & explanation
Correct answer: B. Dry-sump systems allow a larger external oil supply and better lubrication during extreme attitude maneuvers
In a dry-sump system, oil is stored in a separate external tank rather than in the engine crankcase, allowing a larger oil supply and more consistent lubrication during aerobatic or extreme attitude maneuvers where oil in a wet sump might slosh away from the pickup. A scavenge pump returns oil from the sump to the external tank.
Why the other options are wrong
- A. Dry-sump systems still typically use an oil cooler; this is unrelated to the sump design advantage.
- C. Dry-sump systems often use similar or even greater total oil quantity, not necessarily less.
- D. Dry-sump systems require a scavenge pump to actively return oil to the external tank, since gravity alone is insufficient.
Dry-Sump Oil System
An oil system design using a separate external oil tank rather than the engine crankcase, with a scavenge pump returning oil from the sump to the tank, offering better performance during extreme attitudes.
- Oil stored in external tank, not crankcase
- Requires both pressure pump and scavenge pump
- Better suited to aerobatic/extreme attitude operations
- Common in radial and some turbine engines
Memory trick: Dry sump keeps oil in its own tank, so flips and dives don't starve the pump