Military AircrewA forum for the professionals who fly the non-civilian hardware, and the backroom boys and girls without whom nothing would leave the ground. Army, Navy and Airforces of the World, all equally welcome here.
It was reported the other day that the crew of a RN SAR helo elected to fly above VNE in order to reach the scene of a rescue quicker and therefore have more fuel/time on scene to effect the rescue. Surely VNE is VNE or does the RN allow limits to be broken for lifesaving missions?
Moreover apparently having done the job and got the non critical casualty back to base they then refuelled and flew a now potentially unserviceable aircraft again to take him to the local hospital.
Not wanting to start a witch hunt but does this happen often?
I am not military, but deal with SAR on a reglar basis.
Given that they people who fly these missions are the most experienced aircrew in their field, and probably know their aircraft as well as their engineers do, I would say it's judgement call that only they can make, and in doing so they take into account all the factors available to them at the time.
This would not of course, include the judgemental inclusion of hindsight to which you allude to in referring to the casualty as "non critical".
Anybody who busts Vne is a suicidal idiot!!!! Other than mortal combat I can see of NO scenario whereby you could justify exceeding that particular airframe parameter.
Ever seen the picture of the Vulcan that exceeded it? Leading edge peeled off a treat!!
It means exactly what it says on the tin!! But then the Air Farce is full of two-winged idiots who think they know better than the manufacturers eh!!
I was unforunate enough to be sat behind one who took my Herc outside the flight envelope at 250'. Scared that apple tree in the orchard far*less we did!! Provided a spectacular display for the M5 though!!
I would imagine a frame that has been deliberately flown above Vne would be destined for a scrapyard! I certainly wouldn't like to fly in it would you??
No pilot or engineer ever knows the frame as well as the manufacturer. It is the manufacturer who sets Vne!!
Not in the same league, but I remember once being in a bar room discussion with several gliding instructors when the hypothetical question arose, suppose you 'lost' it in cloud or the like, is it better to exceed G-Limits or VNE?
Without fail, all the wise ones said respect VNE and pull that G. The airframe tolerances are usually higher for G limits than VNE which in many case I understand, is set only 5-10 kts below the point at which things start fluttering I gather!
Location: Grobelling through the murk to the sunshine above.
Sadly, Gorilla, life in the human World is not always as simple as it is for you primates.
The phrase "It was reported the other day" throws many variables into the discussion. We must question both the expertise and the motives of the reporter in this case, particularly as he uses the expression 'Vne', which is very seldom used in the helicopter fraternity.
It would be very unusual for a SAR helicopter to be capable of flying above Vne (or its rotary equivalent) in sustained flight. Not quite so unusual for it to be capable of flying above Vmax: an entirely different prospect, which a lot of SAR captains would happily contemplate in life-saving situations. (See 2ndclasscitizen's post)
Thankfully, the human race has evolved beyond the simplistic Gorilla's view, and some of its members are morally and intellectually equipped to make judgements on complex issues.
So let me get this straight In certain circumstances busting and airframe/engine limitation is acceptable based on the scenario presented
Ever wonder how these limitations are derived
VNE, VMAX, VNO, blah blah are exactly that...........so why bust them
Gorrila is quite right to point out that more often than not us "educationally challenged" souls find ourselves hooked on to the gearbox of some medal hunting feckwit who believes his understanding of the airframes limits is far superior to the specialists the manufacturer employs
Location: Grobelling through the murk to the sunshine above.
"In certain circumstances busting and airframe/engine limitation is acceptable based on the scenario presented"
OF COURSE IT IS
SAR crews are frequently faced with this quandary, and they often sacrifice (for example) a little fatigue life in order to help a human one. The decision is based on a multitude of factors, and the crew's knowledge, training and experience can help them make it. Safety of the aircraft and crew is paramount, they all understand that the very worst thing they can do for a survivor/casualty is to become casualties themselves. In my experience these decisions are crew-based and I have never known SAR engineers subsequently to show anything but understanding for their difficult plight.
The vast majority of aircraft engineers are intelligent people who undertsand the operational requirements of their and their aircraft's role. Clearly there are exceptions to this.
The key point is knowledge of the limits, the reasons they were set and the consequences of exceeding the limit. A really good captain will know the above and hopefully make a reasoned decision. Just because a limit is exceeded doesn't necessarily make him a bad pilot.
On a helicopter, maximum IAS limits are set to avoid excessive vibration and a reduction of fatigue life and not for reasons of "aerodynamic flutter". In extremis, depending on type of aircraft, retreating blade stall may also be a limiting factor, subject to all up mass. It isn't really possible to directly compare helicopter limits with those of a glider or any other fixed wing though.
Transmission torque limits are set for similar reasons. In some cases, helicopters transmissions are able to carry quite a bit more torque than the published limit, but at the expense of possible excessive wear. It really depends on the weakest part in the transmission.
If the situation justified it, I would possibly risk the life of a machine to save human life, provided I was sure there was no danger to persons on board. One vital thing is that if a normal limit is exceeded, it must be documented so that corrective engineering maintenance can be carried out if required.
A few years ago I overtorqued a fully laden S-76 because on approach to a newly refurbished and supposedly FOD-plodded and cleared helipad, a hidden piece of wood suddenly flew up in the downwash towards the tail rotor. The crewman screamed that it was going to hit and full power didn't give sufficient avoiding action so adrenalin made me keep pulling until he stopped screaming. The overtorque (fairly large but short lived) was properly written up and no damage was found by the engineers. I was not criticised but then we (7 of us) would possibly have been dead had I NOT exceeded the normal transmision limits.
In order to get certification of a fixed wing design the manufacturer has to NOMINATE a speed for the design known as V design (Vd). If he succeeds in demonstrating in flight that all is well under these conditions then he is REQUIRED to reduce this by 10% and set this lower speed as Vne
Dangerous aeroplanes are those where there is enough power to exceed Vd in level flight or with a small rate of descent that could arise from a moments inattention. There have been one or two examples of this problem in the past and (reasonably) they have attracted a Vne lower than 90% of Vd.
Some aircraft in development programmes get modified for various reasons and this can call for an even lower Vne to be set temporarily. I believe this was one factor in the Vulcan accident referred to earlier.
Please note I am not saying identical rules apply to rotary wing certification as I have never been involved with that. But I would be surprised if the situation with choppers was not similar. Perhaps a rotary wing tp will comment.
Re the RN SAR scenario, we just don't know what happened. Hopefully, if it happened, the reason we know is because the crew came home and owned up.
In extremis, potentially trashing an aircraft, and risking the crew, can be justifiable but the captain had better be prepared to stand up and explain himself whatever the outcome. From personal experience, senior officers with a fixed-wing background, who may see SAR as rather peripheral, are unlikely to understand or be sympathetic.
I took a SK into a situation some would not approached and came away with people who would otherwise have died (smiles all round) but the aircraft was badly damaged in the process. This did not involve exceeding limits (unless of natural caution!) but the implications are similar and the evidence more obvious. I would put this alongside battle damage as "what can happen when you take calculated risks to complete missions" Again, being honest and being able to justify it afterwards is all important.
OBTW, the whole crew discussed the risks in advance and agreed with the plan so let's drop this chip-on-shoulder line about medal-hunting, two-winged master race etc. blah, blah.
As for exceeding aircraft limits, this is not to be lightly undertaken. As for guessing what the designers factored in, forget it. Especially with helicopters, its is an imprecise art and aircrew should treat limits with respect. If it happens, minimise it, get the aircraft back in the hands of the engineers asap, own up and hope it doesn't fall appart two flights later with your mates aboard.
Actually, some rotary Vne limits are set because they cannot be reached without a ridiculous rate of descent being reached, so why bother going faster. eg EC-155 Vne 175 kts, manufacturer has taken it to 210 kts and the head/blades to 240 on a dauphin.
On the other hand, they also take into account the wear and tear on the controls and hydraulic servos; ie componant life consideratioons.
I don't think one can consider exceeding Vne or any other FLM limit deliberately without snagging the aircraft after; not really fair on your colleagues, or you the next time you fly it, really?
It's really quite simple. The rules must be followed. Whenever a crew operates outside the rules, they may be subject to the consequences. With valid reasons to operate there, I'd hope that the consequences would be the exception.
One of the mistakes that is frequently made is the crew isolates themselves. Instead of being a part of a National SAR response, they become, in their mind, the only resource. If your rules, crew or machine is not capable of completing the mission, then perhaps there is another resource that can.
Once you determine that there is no resource, then the outcome of repenting must be compared to the outcome of pressing. Sometimes your best efforts are still not enough. If that's obvious early on, then don't break rules.
You now deem that there is a good reason to operate outside your rules (risk analysis) and there is no other resource to complete the mission. Now is the time to confirm your crew agrees with your plan, and if so execute it.
Sometimes all of the above happens in seconds, sometimes it can happen whilst flight planning on the ground.
I can give examples of exceeding parameters to save lives, exceeding parameters for no good reason, turning down missions that could have been completed by exceeding parameters (some with fatal outcomes), etc. In all but one of the examples, neither I, my peers, nor my superiors found fault in the decisions. In the one exception only a debriefing occurred.
The crews should never feel pressured to go beyond. When a National SAR system is designed, the limitations of the resources would have been considered. A high percentage of mission completion will be a part of the plan, but it won't be 100%.
Time to sum up. SAR crews don't have blanket authority to break rules. If they choose to they must consider other resources, risk analysis, the crew, the machine, and the rules. They mustn't feel pressured to provide what their country has chosen not to provide. All that being said, I think the best way of summing this up comes from our orders:
A too literal interpretation of these orders, that negatively affects the provision of SAR services, was never intended.