Human Performance & Limitations · Module G — The Fit AviatorFitness to Fly
Chapter 17 — The small conditions that ground a pilot: blocked sinuses and barosinusitis, dental barodontalgia and the post-treatment rule, dehydration, personal hygiene, and the common ailments that quietly degrade performance.
Figure 17.1 — The sinuses: a blocked sinus cannot equalise on descent, and the trapped pressure difference causes severe facial pain (barosinusitis).
DGCA-quotedIf the sinuses are congested, then air trapped there can also produce a painful condition. This sinus block occurs most frequently during DESCENT.
Slowing or stopping the descent until the pressure inside the sinus equalizes with the external pressure is the best course of action once this condition occurs.
Of course, NOT FLYING when the pilot has a congested sinus is even better.
Why descent — the same one-way-valve problem as ears (§38.2)
The sinuses are air-filled cavities in the skull (frontal, maxillary, ethmoid, sphenoid) that normally drain through narrow ostia into the nasal cavity. On climb, sinus air expands and pushes outward — easy. On descent, ambient pressure rises and sinus air must contract by drawing more air in from the nose. If the ostium is blocked by mucus/inflammation (cold, hay fever, sinusitis), incoming air cannot enter — a vacuum forms in the sinus → severe pain over the forehead, cheeks or behind the eyes ("sinus squeeze" / barosinusitis).
Mitigation in flight: stop or slow the descent and allow time for pressure to equalise. Prevention on the ground: if you have a head cold, don't fly.
Figure 17.2 — Barodontalgia: gas trapped under a filling or in decay expands as pressure falls, causing tooth pain — hence the 48–72 hour post-dental-work rule.
DGCA-quoted — definitionReduction in atmospheric pressure may also result in BARODONTALGIA — tooth pain.
72.1 Six Dental Conditions That Cause Barodontalgia
DGCA-quoted — verbatim list
This may be caused by a number of dental conditions including:
(a) Dental disease,
(b) Dental caries (a cavity),
(c) Defective tooth restoration,
(d) Pulpitis,
(e) Cysts, and
(f) Impacted teeth.
Mechanism — gas trapped in tooth cavities + Boyle's Law
A small gas pocket under a filling, in a decayed pulp, or inside a sealed cyst expands as cabin altitude rises (Boyle's Law again — §2.1). The expanding gas pushes outward against the tooth nerve → sharp, throbbing pain that becomes excruciating at typical airline cabin altitude (6,000–8,000 ft). It often resolves on descent — but if the affected tooth is fractured by the expansion, the pain persists on the ground.
72.2 The 48–72 Hour Post-Dental Rule
DGCA-quoted — the no-fly ruleThis condition may be avoided by NOT FLYING for 48 – 72 hours following a major dental work.
As with the other problems associated with lower atmospheric pressure, descending to a lower altitude (and correspondingly higher atmospheric pressure) is often the best antidote.
48–72hrNo-fly window after major dental work
6DGCA-listed dental causes of barodontalgia
↓ altIn-flight cure — descend to higher-pressure altitude
Figure 17.3 — Dehydration: dry cabin air, caffeine and poor intake quietly reduce performance — the fix is steady water.
DGCA-quoted
Besides watching what and when they eat, pilots should also be aware of the effects of dehydration. Low fluid intake and dehydration have ADVERSE EFFECTS ON COGNITIVE FLIGHT PERFORMANCE of pilots.
Cross-links — dehydration is everywhere in this chapter
Dehydration has already been flagged repeatedly in earlier parts:
§14 (Alcohol) — alcohol is a diuretic; "masked hangover" includes dehydration.
§23 (Humidity) — cabin RH below 20 % drives over-all dehydration if fluid intake is inadequate; avoid coffee/tea (diuretics).
§28.2 (Fainting) — "standing up quickly after prolonged sitting especially when HOT or DEHYDRATED" is the first DGCA cause of faint.
Practical pilot rule: drink ~250 ml of water every hour during a long sector, regardless of thirst.
§ 74Personal Hygiene
DGCA-quotedA high standard of personal hygiene must be practiced if the body is to remain healthy and free from infection.
Practical implications for crew
Frequent hand washing — particularly before meals and after lavatory use; crew in pressurised, low-humidity cabins are at elevated risk of respiratory infections.
Oral hygiene — directly reduces barodontalgia risk (§72) by reducing the prevalence of caries.
Skin care — low humidity dries skin; lotion/moisturiser reduces cracking that can introduce infection.
Foot hygiene & well-fitting shoes — long sectors with feet on rudder pedals make foot-fungal infections more common in crew.
§ 75Common Ailments
DGCA-quoted — verbatimThe in-flight environment can increase the severity of symptoms which may be minor whilst on the ground. If there is any doubt whatsoever in a pilot's mind about his fitness to fly, he should STAY ON THE GROUND.
The "minor on ground, major in flight" principle
A head cold is a nuisance on the ground; in the air it becomes otic barotrauma + sinus block. A gastric upset on the ground is a meal-skip; in the air the trapped gases expand and incapacitate (§70.2). A mild headache becomes incapacitating under cabin vibration and G-load. The DGCA-codified rule for any doubt is binary: stay on the ground. The cost of a cancelled flight is always less than the cost of a sick pilot in command.
