Many will claim that there is nothing more troubling than a fire onboard a wooden ship at sea. Aviators know there is worst: a fire in flight.
11 years ago I have written an article for the aviation magazine «Plein Vol». It dealt with fires in aircraft. I have decided to refresh this article following refurbishing work accomplished on the PA-30. The issue was an eye-opener.
Abnormal vs emergency
Many malfunctions in flight are considered « abnormal situations ». An engine failure on take-off is abnormal for a multiengine aircraft yet not to be confused with an emergency such as a fire.
Happily modern statistics indicate a relatively low rate of accidents caused by fire in flight. When they do happen, they are understandably quite dramatic. A post accident fire is just as serious business but in a different category. The post accident fire can be understood and dealt with in the same manner, however.
A fire will not declare itself so easily. 3 indissociable elements must be present simultaneously to produce AND sustain combustion. The chain reaction requires oxygen, a combustable substance and an ignition source. Cut off one of the element, you eliminate the reaction.
Typical pilot training will make pilots efficient in dealing with abnormal situations (ie windshear evasion, hydraulics failures and so forth) and emergencies. Smoke and fires emergencies within our QRH (quick reference handbook) provide generic (and proven) procedures: ie engine or avionics bay fires. They are of course dealt with as memory items.
Alas, the one certain fact about fires is that they are unpredictable. Especially the ones hidden behind wall panels or piles of carry on luggage in the overhead bins. As this was not enough they will eventually be the source of multiple failures with no apparent logic when « perceived from the flight deck.
On most turboprops or jets, an engine fire will be detected by the fire detection system. Evidently quick positive action is required to extinguish the fire as many critical systems transit the area! The same applies to wheel well for instance. Keep in mind the average hydraulic fluid flash point is a mere 500˚C.
It is fair to state that an undesirable aircraft state (UAS) will follow should no corrective action be taken promptly or with insufficient emphasis.
Fast identification of a cabin fire is fundamental. Odours will propagate very quickly and are an excellent first indication. For a rule, I never underestimate a flight attendant report even minimal. They are our ears, nose and eyes back there. While flying a smaller aircraft, we are obviously the first to be alerted.
In the flightdeck
Can you imagine the quantity of wiring passing in the area? When this wiring burns and it does, it produces evidently toxic fumes but the smoke. Never neglect the first scanty signs. When smoke powers in, one can forget the capacity to read flight instruments. It is known and demonstrated that heavy smoke is extremely thick to the point of not being able to see your own hands at close range.
Trying to find a critical switch or circuit breaker at this critical moment could prove to be impossible. Try finding an important system switch or CB for the exercise, on the ground of course.
The convergence of high current wiring and ventilation make the flight deck a critical area to control an impending fire. It is absolutely capital that immaculate maintenance be performed without any « unsafe accepted practice ».
The larger the aircraft, the larger risk associated with fires become. The first suspects are galley ovens. Also, impatient smokers are an issue. One can argue that they are « trained » for subversive operations!
A cabin fire must be fought with aggressive action, please note the emphasis on « aggressive ». A fire or smoke source cannot be declared out until all possible elements of the previously mentioned chain reaction are totally eliminated.
Cargo merchandise is a complex issue to manage. Dangerous goods classified by ICAO are not necessarily as such for everyone. As most of us know lithium-ion batteries installed on all consumer electronics, possess flabbergasting property to torch out. Your aircraft is invariably packed with them. Can you imagine carrying a pallet of the stuff? Some years ago when carrying them was permitted an MD-80 suffered a fatal accident caused precisely by this « consumer good » carried as cargo.
Identify, isolate, control, land
There exist no room for complacency. According to the Canadian TSB, an average of 13 minutes only is required between an uncontrolled fire identification and a fatal crash. 13 minutes! In a nutshell: put out that damn fire or land in max 13 minutes.
The human mind can distort reality when under stress. The first thing to do when a situation arises is to designate a timekeeper or just start a chronograph. This is a proven asset to maintain situational awareness. Where you are in time will greatly improve the decision making process. Then promptly isolate the source.
A friendly reminder here on CB’s: if one is hot, there is pretty good chance that you have discovered the faulty system. By the same time if a CB is « popped » leave it opened. It has just performed the work it was designed for in the first place: to electrically isolate a faulty system. Hot panel felt by touching will also reveal good hints. Touch them with the back hand, avoiding burning your palms. You will be handling flight controls shortly!
Renown cases all have common areas of concern: short circuits in big wire bundles, high demand electrical motors such as cabin fans, brakes or overheated tires retracted in the wheel wells.
Once the fire is detected, the adequate manufacturer checklist must be applied. At first glance, this appears to be a no-brainer however it is often messed up due to the difficulty in identification and then with stress going down the QRH items with smoke mask and goggles on. Then get ready, as mentioned earlier, for multiple failures. Wheel well fires such as a B-727 accident in 1986 or a Metroliner in 1998 come to mind.
We can all agree that excellent knowledge of your aircraft systems and procedures are a must, even if one perceives to be irrationally not at risk simply because that very risk is low.
The « proverbial » happens. Trust me …
Another evidence often forgotten: promptly call the emergency. Who cares if one is not certain how that smell will turn out. You can always cancel the emergency later. Who cares about paperwork: it is well worth ones life!
A final word for the fire that was thankfully put out. Do evacuate fumes or smoke. More people get hurt or perish due to smoke ingestion than by the actual flames. The aircraft QRH contains the proper checklist for this.
While on the subject of thinking quickly one should consider airframe integrity. Will it hold up until landing will occur? This within this 13 minutes time frame of course.
Should a fire not be controlled, descent for landing is primordial. To delay descent while burning can well develop into an uncontrollable situation which pretty well might forbid the opportunity of a controlled landing and the required evacuation following a full stop.
The necessity to expedite landing must also not trouble a safe approach. A missed approach with a go-around is simply not an option. « Stabilized » at 170 kts at the FAF (+/- 4 miles final) as opposed to screaming in a 250 kts will only take a few seconds extra time and allow you to stop on the runway thus avoiding further damage and permitting a safe evacuation.
All sort of scenarios, all as improbable as they can be and with unpredictable outcome are the norm. The most common issue is loss of communication, a vital element of sound CRM (cockpit resource management). Radios may be at issue here but think of the two pilots with oxygen masks and smoke goggles on exchanging over the flight deck speaker. It is a mess. Another item here worth mentioning: there is no checklist for hot flight controls. Touching a domestic oven grill at 350˚F provides a good image here.
Flammability of material
Recently while the PA-30 was under interior refurbishing, I decided to test various seat material for flammability. I am told that older aircraft with outdated material are not as flame retardant as modern technology will allow. I can convey to you dear reader that this is by wide margins the understatement of the year. Initially, the refurbishing was planned for occupants comfort. After one of those tests I can certify that the refurbishing was done for safety reasons. I suppose we all suffer from the « out of sight out of mind » syndrome. Not anymore ! Today, fire retardant insulation and seat covering have become quite efficient. But they have to installed to be of any use!
The accident of a now defunct Pilgrim Airlines Twin-Otter in 1982 has also painfully demonstrated the importance of not wearing synthetic clothing. It was found that the alcohol anti-ice reservoir behind the captains seat caught fire. The crew clothing during the inferno was literally melting on their skin adding torture to all other factors involved with flying the aircraft.
« Investment » in the best extinguishers is not a luxury. Nothing replaces so far Halon (1211 or 1301). It will instantaneously destroy the infernal triangle mentioned early on. Halon emanation is toxic but can be ventilated efficiently and no corrosive effect is associated with its use. Our industry benefits from an environmental exemption for the carriage and use. The exemption was probably easy to obtain considering the effect of not using it… Other types of extinguishers (water, powder or CO2) partly work on some various types of fires but are not as efficient and quasi universal as Halon.
Do not hesitate to subscribe to this blog to get the latest from Aviation Common Sense !