rolling take-off
 

I searched the archives but couldn't find anything : AFAIK manufacturers don't deal with rolling take-off in the RFMs. Is there any specific reason for that or is it just because of this check in hover right before T/O - which I doubt ?

ATN

Rolling Take Offs
 

The only RFM that I have seen a running take off recommended was in a 1958 model 'H' Bell 47 with a Franklin engine. When I test flew it in 1978 after an engine change I found out why. This machine was very challenged in the vertical performance department.

Running take offs are a 'limited power' technique and whether you fly a skid machine or wheels don't mess with running take offs unless you have been shown how to do it properly.

For public transport ops you need to ensure you can at least achieve an in-ground-effect hover. If your Tq in-hand is zero you had better be sure you are on a runway or a big field. 5% is a good minimum to work with and 10% ideal. I've thrown pax out before now if the site is a bit on the tricky side. I go back for them later of course - well some of the time anyway.

G
:ok:

Full pax, full baggage, full aux tank, 300nm run, so you know its going to be light enough to land, it just seemed easier to run it down the runway to get through translation without worrying about engine and transmission limits. And to hell with OEI, we'll just operate like any other Class 3.

Otherwise, running takeoffs may be done if you are taxiing towards the helipad, you call tower early 'cause you expect a delay in takeoff clearance and dang, they just come right back and say "cleared for takeoff". Now you are already taxiing at about 15-20 knots, into wind, with a long taxiway ahead of you. Are you going to stop, and then pull into a hover, move over to the helipad, the pull even more power to takeoff? Or just pull a little more collective while you are already rolling and smoothly transition to flight?

One other case for running takeoffs is if your takeoff area is littered and you want to get into the air with the least amount of FOD risk. Hovering only helps to generate a tornado of styrofoam cups, plastic bags, wrappers, paper, etc. Your compressor will love you.

We used to do this alot in the S-61. When your very heavy, full fuel load etc, the ability to conduct a running take off allows you to achieve translational lift on the ground therefore reducing the power required for take off.

T'was generally done by trimming the disc to a hands breadth above the horizon as seen from the pilots seat, pulling to approx 85%-90% Torque and waiting for the aircraft to fly itself off the runway.

I did it on some occasions, mainly during ferry flights, aircraft loaded with gear and extra fuel and it does give a bonus regarding the engine power saved. I have operated with russian crews from an airstrip and never seen any Mi8 or 17 in hover, always departing and arriving on wheels.
The gist of the question was : is there anything - technical, legal or else - preventing the manufacturers to certify this procedure, with prerequisite, weight and power charts, and all ? If there is any logic behind that, I miss it.
I guess the weight should be between the certified MTOW - structural - and the max weight HIGE.
The finality would be to make it officially and legally available.

ATN

I use rolling takeoffs whenever I am departing an airport. Lets me get my 76 off the ground with 60% Tq or less instead of 80%+

Easier on the system, through translational and almost at CDP before the wheels are off the ground.

A couple of pilots I knew who flew S-55Ts for Athabaska Airways used to love doing rolling takeoffs from their base airport - much easier on the machine.

Skids
 

Skids leave some nasty marks on a tarmac, but when you have to, you have to.
Not the greatest feeling in the world if a gusty wind causes you to skid through transition.

The Cobras I flew in Vietnam were about 1200 lbs over gross weight, and the max altitude for hover was about 6 inches. We made sliding takeoffs everywhere, and gained about 10% more payload in the process.

Most helos now are performance designed around the IGE hover, so that MGW matches IGE hover weight under normal circumstances. This means you can't gain payload without busting MGW, even if you make a rolling TO.

But at altitude, it is possible that you can get an advantage. Be careful, it is quite possible then to find yourself in an embarassing position where the landing is a short squatty one as you fall through, if you forget and try to hover. Of course, you will be saved by jumping out and shouting "VRS got me!"

What speed do manufacturers have to certify their undercarriages to withstand ? Could a running takeoff exceed this speed ? If so, the manufacturers aren't likely to stick anything about RTOs into their Flight Manual, because they'd then have to beef up the gear, with all the cost that would entail.
Perhaps.

Used to be taught as a technique by the RAF during the time I instructed, probably still is. I had to do one for real to get a Puma (AS330J) airborne during a single engined transit recovery flight after the second engine refused to start on a small offshore island. It's no big deal provided the surface is OK - we had a small airstrip of oiled rolled sand.

The only times I did it for real, was to leave all the flying dirt behind me on laterite airstrips.
I also use to occasionally practice it, but I don't remember ever been instructed on a particular technique.
I just know I must be carefull with cyclic forward input when taking off.
Since there is no graphs, nor procedure described in the RFM on helicopter type I use to to fly, my common sense tells me it's not an approved technique.

Robbo,
The gear has to meet a percentage of the Vy or Vauto, and must be tested both structurally and handling. It must meet bump and side load criteria, all of which can establish the llimit speed, which should be in the op limits.

I seem to remember that sometime in the 80's the RN were having problems with some cracking in the gearbox support frames (?) of the Sea Kings. The first simple solution, in order to keep operating was to try and restrict operating weight below a certain figure but if not possible, full fuel, weapons etc and above that figure then running take offs were the way to go. Straight forward and no problem if you have a runway etc.

Nick,

Thanks for the info.

Rolling take-offs are the only way to go when you are doing a 0 Vis-0 Ceiling, 600' RVR take-off. Your able to gain some of the speed you need for VToss, VMini (min ifr speed)... while still touching the ground... not a bad place to be.

;)

It's funny how times and philosophies change. Way back in the days of yore, when "yore's" truly got his pilot certificate (endorsed by Wilbur), running take-offs were taught as a matter of course. Franklin's engines (invented by Ben, I'm sure) were not known for their surplus of power, and if you didn't have enough to hover, well, sliding it off was what you did. Sliding it on was more or less a given; you had to assume you wouldn't have enough power to hover. Show of hands, how many of you recall the experience of having the throttle wide-f-open and modulating the RRPM with the collective on take-off? If anyone says they were the "good old days" I will slap you silly.

Nowadays, most helicopters can hover at their MGW and the inability to do so would indicate that los pasajeros have fibbed a little about their personal AUW. Nowadays, at low altitude at least, we wouldn't think of taking off if we couldn't get some air under the skids. Thus, the running take-off/landing techniques have sort of fallen by the wayside.

Most pilots I've flown with make two basic mistakes: First, they try to rush the maneuver; secondly, they move the cyclic much too much.

Obviously, it works better on a helicopter with wheels. But there are dangers. New York Airways used to operate S-61L's (the kind with fixed gear, no sponsons or retractable wheels). Operating out of busy places like JFK, LGA and EWR, the designated landing/take-off areas were not in the terminal areas but out on taxiways- taxiways which were often occupied by largish jets. The helicopter pilots would sometimes "expedite" their landings by "hitting the ground running" instead of coming to a complete stop and setting down. The more comfortable they got, the faster they would touch down. This procedure had tragic consequences later on.

Sikorsky certainly had done their homework on the expected vertical loads for their landing gear. But they never really considered that such strong and repetitive fore-and-aft loads would be imposed. One day, as an S-61 was sitting on the rooftop helipad of the Pan Am Building in midtown Manhattan NYC and passengers were outside of the aircraft, one of the gear legs failed and the ship rolled onto it's side.

Rolling takeoffs aren't a published data chart in the FM for several reasons -
1) there is no regulation that requires it
2) it's not, strictly speaking something you want to be doing.
If you can't hover in ground effect at the height shown for the hover IGE charts, then you've probably overloaded your helicopter for the atmospheric conditions.
It's a great maneuver for teaching coordination, but a lousy lesson on performance (if one day you can't get it into the hover, you can do a rolling takeoff...)
I've been involved in at least one accident investigation where the pilot seriously overloaded the machine at sea level, and then used the rolling takeoff to get airborne. Even an hour or so later, he was still overweight, and couldn't keep it out of the water he was trying to hover over.

Interestingly, the S-61 FLM describes the technique, for either Cat A or B departures, in the Part 1 section 2 (2-28)

I agree that in normal CAT (public transport) operations there is no need for it. Landings though are another story......

In the hot summer of 1969 at MW, the Hiller Ravens of the Basic RW Flight would not lift into a hover with large student (me) and instructor on board. I was taught to apply full power, tilt the disk carefully forward, waggle the pedals to break the grip of the grass, and hope that we got translational lift before we fell into a rabbit hole. Those were the days!

Careful though...
 

Helicopter wheel braking systems are usually designed to prevent the aircraft from moving - not to slow the aircraft or to assist in a taxi turn.

Helicopter braking systems on some (older) types are more prone to overheating, and an overheating brake disc will expand and may seize the wheel concerned.

Airplane brakes ARE designed to slow a fast moving aircraft and therefore have better heat resistant properties.

If the procedure's not in the flight manual.....

Running take offs are still often used by RN Sea Kings in an attempt to prolong the life of those venerable old airframes. It's also an SOP when embarked in an aircraft carrier and the ship can't manoeuvre to generate sufficient relative wind to keep the aircraft within the Ship's Helicopter Operating Limits. It's easier to conduct an aft facing running take off (relative wind permitting), forward facing take offs require the pilot to dodge around the ship's ski jump ramp.

I use rolling take-offs and rolling landings everyday when operating from airports (runways and taxiways).

The simple reason is, for a twin engine wheel equipped aircraft with marginal single engine performance, it is the safest take-off and landing profile in the event of an engine failure. They are not difficult. Every pilot of a wheel equipped twin should be proficient at doing them.

I don't use them to get a heavy machine into the air. That's why we do a weight and balance.:ok:

Hi All,

I used to do rolling take-offs in the 76 from any runway, purely to expedite the take-off. However, since the latest data about the 76 gear and its recurring instances of gear collapse during taxi, I don't think I will be using this practice anymore. Just ask the Air Ambulance drivers in Ontario!

:eek: OffshoreIgor :eek:

S76 landing gear do not have a problem collapsing while taxiing or performing rolling takeoffs or landings.

This was not the cause of the gear collapsing in Ontario.

When spraying with B-47 G-1A and carrying 80 gallons in the heat of the day it's the only way into the air. 60 gallons works a lot better but still never come to a hover. Running takeoff iis so much easier on machine (even with skids).

XNR,

Check the Sikorsky Bulletins on the subject!


Cheers,

:eek: OffshoreIgor :eek:

76 takeoffs
 

Sorry XNR! Gotta disagree!

The safest 76 takeoff is the Cat A within Cat A weights....performance is GUARANTEED. Especially if, as you say, coming off a runway.

The rolling t/o opens up a whole new world of hurt. Just ask some of the OKIE guys about cracked windshields, blown tyres, and such. Also, holding that nose 5degrees down so close to the ground after liftoff can lead to a "situation" when OEI.

The rolling t/o can be used as a risk management "profile" for FOD avoidance.

DK

DK

Don't know why I would be 5 degrees nose down after a rolling takeoff. But you might be 5 degrees nose down as you begin your Cat A.

Of course you could blow a tire rejecting a Cat A as well.

A rolling takeoff is a way of getting the aircraft through translational lift while it's on the ground and a method of getting airborne using minimum power.

There is no requirement for it in performance Category A / Class 1. As I mentioned earlier, the RAF taught it for limited power situations, such as when overloaded or when single engine in a twin.

It's also a safe way of getting airborne in an environment where, if a hover is attempted, the pilot's view might be badly impaired by blowing dust / debris or snow, or a turbine engine might ingest same and be damaged. The advantage is that the aircraft leaves it's downwash behind it.

It's just another a tool in the pilot's toolbox of skills, it's not meant to be used routinely.

Shy

The danger in using them routinely is ........?

XNR,
No danger at all. It is in your bag of tricks, and one of the reasons why wheels are desirable.

The landing gear is not harmed by normal taxi operations, the structural loads are peanuts, unless you are driving around through potholes.

I am surprised at those who think rolling takeoffs "save" the aircraft structure from stresses. The hover stresses are so low they usually cannot be measured, it is the high speed that eats at the aircraft - and I don't think you want to taxi at 150 knots!

I think the key point is not whether the wheels etc are being stressed, it is to what regulations and in what context you are operating. If you are operating to public transport standards using a FLM Cat A procedure, you are effectively entering a grey area by carrying out a running take off, as you have just reinvented the wheel (no pun meant!) The FLM describes the profile used, associated with the take off and rejected take off distances obtained from the graphs, but you are not following it. If you are at the correct WAT weight you will also gain no weight advantage by choosing to do a running take off instead, either.

On the other hand, if you are operating to Cat B, do what you like! Similarly in the military.

The customer's view
 

Just a passing thought that we as pilots should bear in mind.

The debate has identified those situations where the rolling take-off can reduce the problems caused by FOD or snow/sand/dust. We have to concede that this is a judgement-call of the sort we get paid to make.

That said I cannot support the notion that routine running take-offs from runways on public transport flights is a 'good thing'. It's not!

The customer's view is that he wants the helicopter to be operated at minimum risk to his employees (the passengers). This means that you WILL establish HIGE and you will thereby determine that your expectations with regard to the mass of the load carried and the power (Tq) used in the HIGE are realistic and as you expect.

There was a recent case of a 332 being found to be 600lb over the MCTOW after the crew questioned the manifested load from the platform and had it checked after their safe arrival at base.

Mistakes do happen!

I've always thought that what marked chopper drivers out from their ignorant fixed wing cousins is that we have a lot more sense than to sit at the end of a piece of concrete, wind the engines to full chat, let the brakes off and then hope that you will get airborne before the concrete runs out.

Much better that you get airborne first, check all is well, then blast off into the blue.

G

:ok:

Not flying Cat A.....standard configuration......W&B within limits.....do it myself....but the main reason I like to roll on and off is the we have had 2 engines cough their 3rd stage turbine wheels this year.... so if I am already set up to roll it on I really dont care if 1 quits.........well of course I care but it shouldn't hurt me, the other engine or the aircraft.

I hope that as running take-offs are routine in my helicopter operations I am not marked down as ignorant in the eyes of the wider rotary community Geoffersincornwall?

Regards

HEDP

XNR
 

What is your operation?

HEDP

Are we talking C30s?

"Shy

The danger in using them routinely is ........?"

Xnr, I didn't mention danger....why danger?

As Nick said, there isn't one. It might just not be appropriate. If you are operating to Performance A / Class 1 it isn't normally called for. However, to give an example, if I was operating from a runway with blowing snow, I might elect to use the technique to reduce the chance of disorientation from seeing recirculating snow in the beam of the searchlight.

There is a time and a place for everything. Running take-offs and landings with skid equipped helicopters and rolling take-offs and landings with wheeled equipped helicopters are nothing more than another tool in the professional helicopter pilot's tool box.

We practice them in the Apache on nearly every training flight even though rolling take-offs are only used with external tanks and rolling landings would only be used in the even of single engine failure or some other emergency landings. The same is true of all wheeled aircraft.

I have rarely used running take-offs with skid equipped helicopters but have frequently used running landings for both normal and emergency landings.

Helicopter pilots should be able to perform running landings, rolling landings, landings to an IGE hover, landings to an OGE hover and landings to the ground. Each will be used during a helicopter pilots career one time or another depending on the circumstances he/she confronts.

We used to have a single engined ferry alleviation in the Bristow Ops Manual for the Bell 212.

VMC Day Only - 2500ft agl transit for Auto, non hostile terrain.

We therefore practised these at Base Checks - alright on grass but wore the skids out if on concrete/asphalt.

Used to always include the same technique when doing checks on AS355 pilots as I put the same alleviation in PDG's Ops Manual.

I think extended use of imbalanced power into C'Box may be an issue as this may not be covered in gearbox airworthiness certification.

UG :)