BK117
Join Date: Jul 2003
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Love that BK!
The roll to the right is a similar problem to the pitch up. The control rigging doesn't have enough play to counter inflow roll in that condition (right bank / low IAS). Seems like a fairly significant design flaw for a popular production helicopter. Nothing about it in the flight manual either. Still love the machine though, brilliant little workhorse. Any mods known to fix it? Many military users out there?
I have not yet experienced either of these vices operationally, however, i have heard the pitch up discussed over many beers, and the remedy that seemed most popular was to lower the collective. Several whom claim to have experienced the pitch up swear it works a treat.
As for the lasck of cyclic, I too thought it was a right turn. I saw it demonstrated on my endorsement (as I guess ALL BK drivers should have). I believe it is to do with rigging - and in particular, length of the pitch change rods. part of the B2 upgrade was a lengthening of the rods to compensate for this problem, and it does a good job of reducing it's impact - but it doesn't eliminate it altogether. Hopefully you will not experience it in a B2 operationally as it takes some agressive handling to get it into the condition.
Love Monkey (BTW, love the name!!
) you asked the question at the top, and then you answered yourself down here! How did you come across your answer?
And your call that it "seems like a significant flaw" is a big one. I reckon that they have sorted the roll issue out with the B2, and the pitch up seems to be relatively easily compensted for.
As for the lasck of cyclic, I too thought it was a right turn. I saw it demonstrated on my endorsement (as I guess ALL BK drivers should have). I believe it is to do with rigging - and in particular, length of the pitch change rods. part of the B2 upgrade was a lengthening of the rods to compensate for this problem, and it does a good job of reducing it's impact - but it doesn't eliminate it altogether. Hopefully you will not experience it in a B2 operationally as it takes some agressive handling to get it into the condition.
Love Monkey (BTW, love the name!!
) you asked the question at the top, and then you answered yourself down here! How did you come across your answer?And your call that it "seems like a significant flaw" is a big one. I reckon that they have sorted the roll issue out with the B2, and the pitch up seems to be relatively easily compensted for.
Join Date: Jul 2002
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In addition....
I must admit that I too was told the roll issue was normally to the right, but I can’t think of any other reason to explain why the machine reacted the way it did in the left bank.
My understanding of the situation was limited to the ‘results’ as apposed to the ‘cause’.
Out of a vested interest - Is there evidence that suggests it couldn’t happen to the left? And wouldn’t the ‘nose high’ situation, stated above as possibly being the same thing, suggest it could happen at any attitude?
My understanding of the situation was limited to the ‘results’ as apposed to the ‘cause’.
Out of a vested interest - Is there evidence that suggests it couldn’t happen to the left? And wouldn’t the ‘nose high’ situation, stated above as possibly being the same thing, suggest it could happen at any attitude?
Join Date: Sep 2002
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Severe nose pitch up at high IAS/AUW/DA and corrected by lowering collective;...... Please correct me if this is a really ignorant and simple answer to a more complicated problem, but aren't these clasic retreating blade stall symptoms?
Join Date: Apr 2003
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BK pitch-up
I have seen the pitch-up on an almost regular basis when above about 10,000 DA and at high AUW and pushing the machine along at close to VNE for the conditions, but never seen it at low DA, AUW, or speeds.
I have always assumed that the pitch up was being caused by retreating blade stall. Lowering the collective certainly helps correct the pitch up which is consistant with the recovery technique for retreating blade stall as well.
I have always assumed that the pitch up was being caused by retreating blade stall. Lowering the collective certainly helps correct the pitch up which is consistant with the recovery technique for retreating blade stall as well.
Join Date: Dec 2001
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BO-105 has a control box (Cyclic range of movement) that is rectangular in shape. The rectangle runs longitudinally and is offset to the right, so there is less cyclic movement to the left than right.
This equates to: low speed steepish turn to the right, move cyclic left to roll out and hit the cyclic left stop... There is enough cyclic to reverse the turn, but takes time.. With low altitude.. time equals height and a very spectacular PRANG....
Rule # 1 in BO-105.. Low level turns are always to the LEFT...
Cannot recall if BK has the same problem.. (Don't thinks so mind you)
This equates to: low speed steepish turn to the right, move cyclic left to roll out and hit the cyclic left stop... There is enough cyclic to reverse the turn, but takes time.. With low altitude.. time equals height and a very spectacular PRANG....
Rule # 1 in BO-105.. Low level turns are always to the LEFT...
Cannot recall if BK has the same problem.. (Don't thinks so mind you)
I believe this is a similar handling quirk to that of the Lynx and is common to many helis with 'rigid' ie high hinge offset rotor heads.
It would take the venerable Nick Lappos or demi-god Shawn Coyle to explain it correctly but in normal flight conditions the rigging, advance angle, pitch horn position et al can be arranged to match the phase lag (not usually 90 degrees with high hinge offset rotors). This means that where you move the cyclic, the rotor will obediently follow.
But when you start to manoeuvre the heli, especially in a tight turn the dynamics of the rotor response produce a pitch-roll coupling because the phase lag is no longer perfectly matched to the rigging - so when you pull back on the cyclic the rotor pitches up but also rolls right forcing you to oppose the motion with left cyclic. Now you are in a right turn with left cyclic applied, meaning your control margins for rolling out have been seriously reduced.
This phenomenon is very noticeable on the Lynx in high AoB turns, quickstops, wingovers and pitching display manoeuvres (back flip, loop etc that are flown AFCS out)
It would take the venerable Nick Lappos or demi-god Shawn Coyle to explain it correctly but in normal flight conditions the rigging, advance angle, pitch horn position et al can be arranged to match the phase lag (not usually 90 degrees with high hinge offset rotors). This means that where you move the cyclic, the rotor will obediently follow.
But when you start to manoeuvre the heli, especially in a tight turn the dynamics of the rotor response produce a pitch-roll coupling because the phase lag is no longer perfectly matched to the rigging - so when you pull back on the cyclic the rotor pitches up but also rolls right forcing you to oppose the motion with left cyclic. Now you are in a right turn with left cyclic applied, meaning your control margins for rolling out have been seriously reduced.
This phenomenon is very noticeable on the Lynx in high AoB turns, quickstops, wingovers and pitching display manoeuvres (back flip, loop etc that are flown AFCS out)
For you BO and BK drivers....ever try to fly the aircraft using collective movements to control roll? In cruise flight....roll attitude can be controlled by use of the collective if you are patient and catch on to which way the aircraft reacts to those collective movements. That will demonstrate much of what Crab is saying about cyclic/collective roll coupling.
SASless:
"...In cruise flight." Heh. Not in a Boelkow, old boy. Cruise flight in a 105 (around 120 knots) is denoted by a healthy 8 - 10 degree nose-down pitch attitude. At such an attitude, leaving the cyclic unattended for any length of time results in the a/c trying to turn itself inverted.......regardless of what you do with that lever next to the seat. I've flown a lot of different 105's (including some that their regular pilots proclaimed to be "very stable"), and NONE of them would stand more than about 9 or 10 seconds of hand-off-the-cyclic before departing S/L flight no matter how well-trimmed I could get it.
At 60-70 knots however, it is fun to fly the BO by using the collective alone. At those speeds it is "relatively" stable, although I laugh at the very thought of using the words "stable" and "Boelkow" in the same sentence.
I had an amusing conversation with a Boelkow pilot once. It enlightened me as to how fiercely loyal and unobjective pilots can be about their aircraft. This guy was going on and on about how wonderfully stable the 105 was. I was chuckling to myself and shaking my head. When he finally stopped to take a breath, I managed to interject my little discovery about how they'll start to go upside down in an average of seven seconds if you take your hands off the cyclic. He immediately replied, "Yeah, they do that."
This man obviously had no earthly idea what constituted "stability" as it applies to helicopter flight.
His "solution" was novel. "What power-setting do you fly at?" he asked. I said, "120 knots, and whatever it takes to get me there." He then said, "Well that's your problem! You're cruising too fast. Slow it down to 100 knots and it's VERY stable."
He was dead serious too, as far as I could tell. I think he was trying to get me to believe that when he flew the 105, he drove around at 100 knots watching everything from Astars to 407's blow by him. Sorry chaps, but I've spent my life in 70 knot Bell 47's, 90 knot 206B's and 104 knot 206L's. I'm not about to reign in a ship that can "scoot" at 120. And I don't think most other 105 pilots do either.
And for the record, the 105 isn't all that much more stable at 100 knots than 120. It's better......but that's not saying much.
For you BO and BK drivers....ever try to fly the aircraft using collective movements to control roll? In cruise flight....roll attitude can be controlled by use of the collective if you are patient and catch on to which way the aircraft reacts to those collective movements. That will demonstrate much of what Crab is saying about cyclic/collective roll coupling.
At 60-70 knots however, it is fun to fly the BO by using the collective alone. At those speeds it is "relatively" stable, although I laugh at the very thought of using the words "stable" and "Boelkow" in the same sentence.
I had an amusing conversation with a Boelkow pilot once. It enlightened me as to how fiercely loyal and unobjective pilots can be about their aircraft. This guy was going on and on about how wonderfully stable the 105 was. I was chuckling to myself and shaking my head. When he finally stopped to take a breath, I managed to interject my little discovery about how they'll start to go upside down in an average of seven seconds if you take your hands off the cyclic. He immediately replied, "Yeah, they do that."
This man obviously had no earthly idea what constituted "stability" as it applies to helicopter flight.
His "solution" was novel. "What power-setting do you fly at?" he asked. I said, "120 knots, and whatever it takes to get me there." He then said, "Well that's your problem! You're cruising too fast. Slow it down to 100 knots and it's VERY stable."
He was dead serious too, as far as I could tell. I think he was trying to get me to believe that when he flew the 105, he drove around at 100 knots watching everything from Astars to 407's blow by him. Sorry chaps, but I've spent my life in 70 knot Bell 47's, 90 knot 206B's and 104 knot 206L's. I'm not about to reign in a ship that can "scoot" at 120. And I don't think most other 105 pilots do either.
And for the record, the 105 isn't all that much more stable at 100 knots than 120. It's better......but that's not saying much.
Sasless, as you say this use of collective demonstrates the pitch roll coupling common to many 'rigid' rotors because the raising of the lever causes the disc to flapback (instability with AoA and true of all helicopters). The resultant roll or lack of it will tell you if the phase lag is 90 degrees or not (as mentioned earlier it reduces with effective hinge offset).
Join Date: Apr 2002
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bk117
Anyone know where I can find out how many BK 117's have been produced and how many were C1's.
I hear the last one is in production and sold to Italy.
Are there any operating in the UK?
I hear the last one is in production and sold to Italy.
Are there any operating in the UK?
Try www.Rotorhub.com it has links to production lists.
They are not 100% accurate but they will give you good idea.
I will now go and wash my mouth out with salt for promoting that that is not mine!
They are not 100% accurate but they will give you good idea.
I will now go and wash my mouth out with salt for promoting that that is not mine!
Join Date: Mar 2002
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Kawasaki BK117 A4
Don't know much about BKs so I'm after someone that can give me more info about the models, usable payload, range, external load capacity, pax numbers etc.
There must be many a pilot out there that can help me.
Which is the best(not necessarily newest) BK model out there(excluding the C2/EC145)
Thanx in advance for your help
There must be many a pilot out there that can help me.
Which is the best(not necessarily newest) BK model out there(excluding the C2/EC145)
Thanx in advance for your help
Join Date: Dec 2002
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Best model would have to be tha Bk117B2 with all ADs and SBs complied with... including the installation of the C mod tailrotor. ...
...If you go ahead and get one(?) try to get (buy, beg ,borrow or steal) the tooling to set up the tailrotor hub (fork) bearings.
Enjoy.......
...If you go ahead and get one(?) try to get (buy, beg ,borrow or steal) the tooling to set up the tailrotor hub (fork) bearings.
Enjoy.......
Join Date: Jun 2003
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BK117 A4 modified to B2
LTS 101-750B1 engines (750 HP)
Payload max gross 3350kg up from 3200kg
Max gross with external load 3500kg (up by 300kg)
Improved CAT A performance up to 280kg higher payload
Upgrade kit for A4 to B2 includes
Uprated engines (750 hp)
new T/R blades (improved design)
Increased pitch range of MR blades
Uprated OEI Main gearbox limit (2.5 min limit up from 100% to 125%)
New engine instruments (different limit ranges)
To upgrade from A1 or A3 to B1 the A/C must first be upgraded to A4 model
I believe the A1 and A3 had the 650 HP LTS these had quite a few problems and were often removed for inspection every service. Not a problem now with the 750 it has new GP Turbine Disc (single crystal) stopped cracking problem.
You may find that some A4s have been upgraded with the 750hp engine but have not been upgraded to a B2 because the kit can be quite expensive... I have heard that the torque gauge costs at least 20k US.
There have not been many major airframe mods throughout the range mainly engine mods to upgrade.
So the best bet may be to purchase an A4 and upgrade to B2 for a pretty good performer.
As for PAX you can have 8 in the back and 2 crew for a full load or may other variations of seating as required.
Max hook load is 1500kg but I think you would be lucky to lift about 1100Kg on average.
LTS 101-750B1 engines (750 HP)
Payload max gross 3350kg up from 3200kg
Max gross with external load 3500kg (up by 300kg)
Improved CAT A performance up to 280kg higher payload
Upgrade kit for A4 to B2 includes
Uprated engines (750 hp)
new T/R blades (improved design)
Increased pitch range of MR blades
Uprated OEI Main gearbox limit (2.5 min limit up from 100% to 125%)
New engine instruments (different limit ranges)
To upgrade from A1 or A3 to B1 the A/C must first be upgraded to A4 model
I believe the A1 and A3 had the 650 HP LTS these had quite a few problems and were often removed for inspection every service. Not a problem now with the 750 it has new GP Turbine Disc (single crystal) stopped cracking problem.
You may find that some A4s have been upgraded with the 750hp engine but have not been upgraded to a B2 because the kit can be quite expensive... I have heard that the torque gauge costs at least 20k US.
There have not been many major airframe mods throughout the range mainly engine mods to upgrade.
So the best bet may be to purchase an A4 and upgrade to B2 for a pretty good performer.
As for PAX you can have 8 in the back and 2 crew for a full load or may other variations of seating as required.
Max hook load is 1500kg but I think you would be lucky to lift about 1100Kg on average.
TD,
Picking at nits, but the max hook allowable on the 117B is 1300kg, and the upgraded Tq is an option, not a standard on the B2. Fairly expensive, as you say, requiring replacement Tq gauge & upgraded transducers (4 off), plus rescheduling of the FCU (IIRC, I'll have to check later). Similarly, the tail rotor blades are off the 117C model, and not a standard mod for -B2 upgrade. Really nice to have, though, and make a stunning difference to the aircraft, especially heavy and/or high altitude. With the standard tail rotor blades, cramp in the left calf was almost commonplace with all that left pedal needed, but I can only think of one or two occassions that the T/R has approached full left since we upgraded to the -C tail rotor.
Regardless of all the times that various Authorities tell us to only buy from manufacturers or OEI suppiers, a cautionary tale. When we fitted the -C TRB's, we also had a tail rotor assembly, complete from Eurocopter. On the first run, the pedals required 20-30lb force to hold neutral, and Eurocopter's response was along the lines of "get used to it, not our fault, there's a 117 in NZ the same problem, pilots hate it".
After a lot of checking, it turned out the factory had assembled the tail rotor hub using Bo105 weight arms
When the correct parts were supplied, all became sweetness and light 
DC,
Fuel consumption about 300lt/hr, or 240kg/hr. DOC, and known aircraft for sale, PM or e mail me
Picking at nits, but the max hook allowable on the 117B is 1300kg, and the upgraded Tq is an option, not a standard on the B2. Fairly expensive, as you say, requiring replacement Tq gauge & upgraded transducers (4 off), plus rescheduling of the FCU (IIRC, I'll have to check later). Similarly, the tail rotor blades are off the 117C model, and not a standard mod for -B2 upgrade. Really nice to have, though, and make a stunning difference to the aircraft, especially heavy and/or high altitude. With the standard tail rotor blades, cramp in the left calf was almost commonplace with all that left pedal needed, but I can only think of one or two occassions that the T/R has approached full left since we upgraded to the -C tail rotor.
Regardless of all the times that various Authorities tell us to only buy from manufacturers or OEI suppiers, a cautionary tale. When we fitted the -C TRB's, we also had a tail rotor assembly, complete from Eurocopter. On the first run, the pedals required 20-30lb force to hold neutral, and Eurocopter's response was along the lines of "get used to it, not our fault, there's a 117 in NZ the same problem, pilots hate it".
After a lot of checking, it turned out the factory had assembled the tail rotor hub using Bo105 weight arms
When the correct parts were supplied, all became sweetness and light DC,
Fuel consumption about 300lt/hr, or 240kg/hr. DOC, and known aircraft for sale, PM or e mail me