Rotorcraft v Fixed Wing Accident Rates

[er340790]

PPL here.

The organisation I work for is considering replacing a Cessna R172 with a Robinson R44. Part of the business case for the purchase requires an assessment of the relative risks of operating the two aircraft.

Does anyone know of any published stats that can be reliably quoted (no hear-say) for rotorcraft v fixed wing accident / fatality rates. I have some NTSB data from the mid 90s, but nothing bang up to date. (For anyone interested, that raw data suggested a 25% higher fatality rate per 100,000 operating hours.)

Yes, bear with me, I know the S&R / Emergency use of helicopters in hazardous conditions often results in skewed 'accident' figures, but I need the hard actual data for others to draw conclusions from.

Many thanks!

[ATPMBA]

Get a B206 Jet Ranger

I heard it is the safest single-engine AIRCRAFT in the world and the NTSB has the stats to back it up.

[Gomer Pylot]

What you want is hard to quantify. The two types of aircraft aren't operated in the same way, in the same places. Helicopters typically tend to use unprepared landing sites, or sites that have obstacles, because otherwise they have little utility. If you're going to operate only from airports, then a fixed-wing makes much more sense, because they're far cheaper to own and operate. Flying out of unprepared sites is inherently more dangerous, but also provides more utility, and potentially more profit. Straight accident statistics don't give the full picture.

[What Limits]

Here (http://www.tsb.gc.ca/en/stats/air/2007_dec/a12_2007_e.pdf) are some accident figures from the TSB in Canada, they are not accident rates though so be careful how you use them.

[Helinut]

As Gomer Pilot says, it is doubtful whether overall stats FW v RW will give you what you need. By their nature stats are average for the range of operations and types that they cover, Whatever your operation is will likely veer far from that "average" reflected in the stats.

[What Limits]

Also if you are going to do the same role, then the risks are very much the same anyway.

[Shawn Coyle]

What's the mission? That will make a huge difference in the risks. Rather than a comparison of the accident rates, (the C172 will not fare well due to the low time of most pilots flying them), why not a detailed analysis of the mission and the risks, etc.

[helmet fire]

I agree with all the above, comparison of accident rates per 100,000 hours will be at best irrelevant, and at worse completely misleading.

if you want to compare risk levels alone as against to other factors such as cost/speed/payload) then you need to compare the types over the same mission profile. Accordingly, compare them from airport to airport and VFR.

The single biggest risk will be CFIT. The R44 wins this comp because it can slow down to cope with poor weather, and conduct a forced landing almost anywhere. The 172 is committed to remain above stall speed and must find a rare piece of ground if it is to conduct a forced landing. Assuming you keep the same weather minima of course!

The next would be pilot error on take off and landing, which will be too difficult to consider given the volume of low pilot experience accidents in the 172.

Next is engine failures. Assuming the exact same failure rate (which they are not!) the R44 again wins as an auto is almost always going to be more successful than an engine off in a light aeroplane to the same piece of ground from the same failure height. Not ALWAYS, but almost always!

Next is probably fuel systems (though this is likely to be higher likelihood than engine failures). Both are pistons, both get same fuel from same source so risk due fuel quality is identical. Other failures would be too infrequent to form valued comparisons between the types, though fuel mismanagement would be far more common in the 172 due to the lower pilot times and the fact that even if you really blow it in the R44 the consequence is a forced landing - safer in the R44.

Finally would be structural failures. You would have to research these, but they would be extremely rare on either type.

Conclusion: over the same mission profile the R44 represents the lowest risk by a considerable margin.

Problem is people buy the R44 and start reducing the safety buffers offered by the R44 such as accepting poorer weather, conducting landings to unprepared HLS, skimping on fuel quality because you know you are more likely to land safely if it is wrong, or even reducing your fuel planning margins for the same reason. This fundamentally invalidates your risk comparison and may lead to the R44 equalling or exceeding the 172 in terms of residual risk.

And this is where we look at the extra mission benefits and begin to evaluate risk V gain for accepting them. A whole other topic!

clear as mud?

[ReverseFlight]

Listen to ATPMBA. Get a real helicopter if you really need one.

If you don't need a helicopter, get a fixed wing instead.

My 2 cents worth. Safe flying.

[JimL]

Perhaps the answer to the question about the relative safety of helicopters/fixed wing can be found in a paragraph to the Judgement that Ian Evans has just made available to us. This can be found in Paragraph 4.96 on Page 54.

A total of 130 accidents occurred among US air carriers in 2003 which was comprised of 54 Part 121 accidents, two scheduled Part 135 accidents and 74 on-demand Part 135 accidents. In 2003 air carriers flew more than eight billion miles, recorded at least 11 million departures and logged almost 23 million flight hours. The report shows that Part 135 helicopter operations accounted for 800,000 hours flying and 36% of the total accidents in that class. The remaining two million hours were flown by fixed wing aircrafts and which had 64% of the total accident. Proportionately, helicopter flying was more than 1.5 time more likely to lead to an accident than fixed wing flying in Part 135 operation. This amounted to 22.7 accidents per million hours in fixed wing aircraft and 34 accidents per million hours for helicopters. Further, the proportion of all accidents that were fatal for helicopters was also three times higher than for fixed wing at 12.6% as against 3.9%. Part 121 multi-crew operations were more than 10 times safer than Part 135 operations with respect to injury rates of 3% and 43% respectively. Twice as many people were fatally injured in helicopters as in fixed wing aircraft.
Jim