N999LJ Learjet 60 crashes on take-off SC.
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If both Sqk switches are not on the ground then aircraft is on AIR mode, so no TR, no Autospoiler deploy and no Antiskid. The 60 only get info from there, no wheels spinning sensor. Now, 1 mile is a lot, but with no brakes is not that much.
About normal take off flap is 8°, 20° is used only on short fields, you can get 400-500 feet less of take off roll with flap 20, I only used once 20° on my trainning at FSI.
About normal take off flap is 8°, 20° is used only on short fields, you can get 400-500 feet less of take off roll with flap 20, I only used once 20° on my trainning at FSI.
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Not quite accurate...
Learjet Service Bulletin SB 60-78-7 modifies the aircraft to allow the T/Rs to receive an input from the wheel speed detect box (used for autospoilers). This would prevent an inadvertant stowing should the squat switch be damaged during landing/aborts.
The danger of an uncommanded stow following a squat switch failure is that the FADEC will initially command the engine to idle, then to whatever power setting is requested at the thrust levers after the T/Rs stow. The "piggy-back" levers, if still pulled aft, would be commanding a high power setting of the FADEC (which believes the aircraft is airborne and just stowed a T/R). I believe that the piggy-backs move the same linkage as the thrust levers do to a rotary switch that is interpreted as a thrust lever angle by the FADEC, thus giving up to nearly takeoff power while you tried to stop. This scenario would be good if you really had a T/R deploy while airborne, but can be horrible if it happened on the ground.
The AFM has a Emergency Procedure (as a Memory Item) that instructs you to close the piggy backs should a T/R stow by itself to prevent this situation
Also, the above SB did not apply to N999LJ based on serial number, so I assume it had it installed.
Learjet Service Bulletin SB 60-78-7 modifies the aircraft to allow the T/Rs to receive an input from the wheel speed detect box (used for autospoilers). This would prevent an inadvertant stowing should the squat switch be damaged during landing/aborts.
The danger of an uncommanded stow following a squat switch failure is that the FADEC will initially command the engine to idle, then to whatever power setting is requested at the thrust levers after the T/Rs stow. The "piggy-back" levers, if still pulled aft, would be commanding a high power setting of the FADEC (which believes the aircraft is airborne and just stowed a T/R). I believe that the piggy-backs move the same linkage as the thrust levers do to a rotary switch that is interpreted as a thrust lever angle by the FADEC, thus giving up to nearly takeoff power while you tried to stop. This scenario would be good if you really had a T/R deploy while airborne, but can be horrible if it happened on the ground.
The AFM has a Emergency Procedure (as a Memory Item) that instructs you to close the piggy backs should a T/R stow by itself to prevent this situation
Also, the above SB did not apply to N999LJ based on serial number, so I assume it had it installed.
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From my memory...
1. Yes and No. Damage to the squat switches (which are located on the top of the main gear scissors facing forward) should provide an airborne signal and will render ANTISKID inoperate. I am not positive about the Lear-60, but on older Lears with the same system, the left Squat Switch controls the outboard brakes, the right controls the inboard. Turning the Anitskid OFF should restore brakes, though without the antiskid protection.
2. No. The T/Rs need (among other things) a GROUND signal from both of the squat switches to ARM (happens automatically upon touchdown) unless the aircraft has the above mentioned Service Bulletin which would use wheel spin-up instead. Should they not ARM, nothing would happen if the crew tried to pull back on the Piggy back levers as a balk would prevent their movement beyond the Idle position. They would physically move far enough to try to deploy, but not far enough to increase thrust, if that makes sense.
3. Yes, they are hydraulically boosted. The two lines (inboard and outboard brakes) run down the front of the oleo strut, then snake around one side (outboard, I believe...and above the outboard tire) to the aft portion of the strut, then arc aft between the tires entering the calipers from the rear. The antiskid wiring is also routed the same way. I feel that it is very likely that tire debris could damage the lines, especially if it was the outboard tire that failed.
See http://www.airliners.net/photo/Arkas...-60/1397847/L/
The squat switch is the circular object just below the landing light.
1. Yes and No. Damage to the squat switches (which are located on the top of the main gear scissors facing forward) should provide an airborne signal and will render ANTISKID inoperate. I am not positive about the Lear-60, but on older Lears with the same system, the left Squat Switch controls the outboard brakes, the right controls the inboard. Turning the Anitskid OFF should restore brakes, though without the antiskid protection.
2. No. The T/Rs need (among other things) a GROUND signal from both of the squat switches to ARM (happens automatically upon touchdown) unless the aircraft has the above mentioned Service Bulletin which would use wheel spin-up instead. Should they not ARM, nothing would happen if the crew tried to pull back on the Piggy back levers as a balk would prevent their movement beyond the Idle position. They would physically move far enough to try to deploy, but not far enough to increase thrust, if that makes sense.
3. Yes, they are hydraulically boosted. The two lines (inboard and outboard brakes) run down the front of the oleo strut, then snake around one side (outboard, I believe...and above the outboard tire) to the aft portion of the strut, then arc aft between the tires entering the calipers from the rear. The antiskid wiring is also routed the same way. I feel that it is very likely that tire debris could damage the lines, especially if it was the outboard tire that failed.
See http://www.airliners.net/photo/Arkas...-60/1397847/L/
The squat switch is the circular object just below the landing light.
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The 60 allows the inboard or outboard anti-skid to continue working with just one operative squat switch in "ground" mode. You're right about turning the anti-skid "off" though. That gives you braking regardless of squat switch signals. So does emergency braking.
But of course, you might blow tires without anti-skid on a heavy plane with such little wheels and brakes.
But of course, you might blow tires without anti-skid on a heavy plane with such little wheels and brakes.
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Read that tire blowouts were becoming more common due to crew just not checking tire pressures. In a charter/fractional environment, I know the pilots don't carry tire guages as a rule...
Tire blow outs- Seems to be the bane of those that like to burn up runways, either overgross, Flex, or just not use all available flaps to get off quick.
You're still beating this reduced thrust drum, still don't get the concept...even after it's been explained to you time and time again. You're trying so hard not to get banned this time, but you really can't help yourself...you're stuck on this topic and it's just killing you, isn't it?
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Ahhh Guppy....your such an tool....Still living in a world where tires don't blow out and V1 guarantees all planes fly??...Go run to the moderator Guppy...ban everyone that disagrees with you...You know Guppy...tires still come apart with fuse plugs(surprise, surprise)...they call them blow outs...ever heard of those?..or does your world only consider the fuse plug slowly and safely deflate the tires, how nice........tell that to the Concord folks....Check 6...welcome to Guppy world, you will get along just great here...I guess in your world, only the A/Ps have tire guages...unbelievable...!@#@$@
Ah, SSG V1.10
Tire checks are for mechs unless away from base with no maintenance available and trained. My plane, mains at 185 -0, +5; if I check the tires and the pressure is at 185, what is it when I remove the gage and a little nitro escapes?? Less than 185, correct? If I check them daily, in a few checks, it will be low. Check the tires where MX is available, every time. I had one blow at about 90 knots, airborne, checked the gear, returned. Best solution, esp when there are 27 more!!
GF
Tire checks are for mechs unless away from base with no maintenance available and trained. My plane, mains at 185 -0, +5; if I check the tires and the pressure is at 185, what is it when I remove the gage and a little nitro escapes?? Less than 185, correct? If I check them daily, in a few checks, it will be low. Check the tires where MX is available, every time. I had one blow at about 90 knots, airborne, checked the gear, returned. Best solution, esp when there are 27 more!!
GF
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I just returned from the beautiful memorial service at Palomar Airport for Jim. Sarah's service was held also today in Washington. Jim was held in high regard by all those who knew him. I am all for dignified professional discussion however, I personally am not going to guess on the cause of this unfortunate event. I will wait for NTSB's report.
Several times while on US Customs missions late at night, Jim flew over my house well after airport curfew chasing a suspected smuggler into LGB. My house is about 10 miles out from runway 30 at LGB on the extended centerline. I'd call him the next day & ask, "Was that you in the Citation at about 0100?" Jim would always give me the hot scoop. During his time at US Customs, Jim was involved in almost every major smuggling case involving the San Diego office. From time to time I would wake up very late at night and hear a jet passing very high in the distance. I'd often wonder if it was Jim.
I'd ask everyone that if you wake up late at night & hear a distant jet, please think of Jim as he now patrols the skies for eternity.
Several times while on US Customs missions late at night, Jim flew over my house well after airport curfew chasing a suspected smuggler into LGB. My house is about 10 miles out from runway 30 at LGB on the extended centerline. I'd call him the next day & ask, "Was that you in the Citation at about 0100?" Jim would always give me the hot scoop. During his time at US Customs, Jim was involved in almost every major smuggling case involving the San Diego office. From time to time I would wake up very late at night and hear a jet passing very high in the distance. I'd often wonder if it was Jim.
I'd ask everyone that if you wake up late at night & hear a distant jet, please think of Jim as he now patrols the skies for eternity.
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If I check them daily, in a few checks, it will be low.
All light vehicles in the US are now manufactured with TPMS onboard. Some aircraft are still being manufactured without such a system. Such systems are much better than relying on humans for such a task which tends to be unimportant and boring most of the time except for when it makes all the difference in the world.
SkiMan
Cite an FAR 25 plane with TPMS? No business jet has it, maybe should, but doesn't
Yes, we can check the pressures, but it there is no nitro cart, how am I going to service them. But, in any case, we only identify the problem, tech does the servicing. BTW, these are airplanes, not my car, not trained, not doing it.
GF
Cite an FAR 25 plane with TPMS? No business jet has it, maybe should, but doesn't
Yes, we can check the pressures, but it there is no nitro cart, how am I going to service them. But, in any case, we only identify the problem, tech does the servicing. BTW, these are airplanes, not my car, not trained, not doing it.
GF
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gf: A380. On the bizjet side, the Falcon 7X. Both from Messier-Bugatti. Seems like a good idea, no?
On the blown tire front, we also fly Sabreliner 65s, which have single main wheels
.Theit AFM procedure is always to take the airplane flying with a blown tire above 100knots. Nuts to that!! It's 80 knots for us unless we're at KIAD or someplace like that where runway is virtually a non-factor .
One thing for us all to consider is: Was the crew trained for blown tires at various takeoff speeds? What do their company ops specs say? I taught the Falcon 2000 and 900EX Easy for 4 years and it was amazing the responses I saw in the sim, and how many high time crews had never been trained with it. A blown tire could cause so much vibration that a crew might mistake it for an airframe problem and not want to go flying under any circumstances. It's been implied that this crew thought that they has a blown tire, but we don't have any time line yet as to when brakes were applied etc. The NTSB will sort that out.
At any rate it's tragic when a good crew does everything that they can under any circumstance and it's not enough.
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It is with proper respect and sympathy I ask the following questions...I'm sure it will be awhile before we really know what happened.
1. Was there any discussion in the cockpit about course of action? If so, who said what?
2. What is the Flight Safety, or other group where these pilots trained, sylabus item and actual training for tires blown on takeoff? ARE THEY TRAINED TO GO AT 80Knots?
Another poster indicates that they knew the captain and was part of training at Flight Safety. I hope that person can answer number 2 above.
1. Was there any discussion in the cockpit about course of action? If so, who said what?
2. What is the Flight Safety, or other group where these pilots trained, sylabus item and actual training for tires blown on takeoff? ARE THEY TRAINED TO GO AT 80Knots?
Another poster indicates that they knew the captain and was part of training at Flight Safety. I hope that person can answer number 2 above.
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2. What is the Flight Safety, or other group where these pilots trained, syllabus item and actual training for tires blown on takeoff? ARE THEY TRAINED TO GO AT 80Knots?
The answer to your question is a qualified "yes".
The "standard" FSI briefing is to "Abort for any malfunction up to 80knot, after 80 knots only abort for engine fire, engine failure, thrust reverser deploy or loss of directional control".
Now does a blown tire have with it the consequence of "loss of directional control"? If so, the crew would have been taught to abort beyond 80 knots, depending upon what their SOP says. If companies, especially those operating under FAR 135, have their own SOPs, FSI instructors are expected to become familiar with, and use those criteria in training and checking.
I will ALWAYS disagree with the concept of making that 80 knots "dividing line" boilerplate, since there are so many other factors in takeoffs, including excess runway length that have to be considered. In the Falcon 900 we would rarely think of taking ANY problem airborne prior to V1, simply because the V1 speeds are very low (less than 110kts at normal operating weights) and the brakes, emergency braking system and tires are so overbuilt. Runways over are usually not an issue since at gross weight ISA and SL the runway requirement for the 900 is only 5,390 feet. This is pretty insignificant, especially compared to the Lears.
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Good question. I couldn't tell you what Vmu is for any Lear. I don't believe I've ever seen it published since it's a certification number rather than an operational one.
Other than per FAR 25, it has to be equal to or greater than Vs, I can't offer much.
I do think that the problem still lies with the way that we train in bizjets. Because the FAA's infinite wisdom dictates that examiners and instructors concentrate on "filling the squares" of the Practical Test Standard, training in maneuvers like tire failure is generally not a priority. The fact is, that there is already so much to cover(much of it BS) that many instructors are always trying to put 20 gallons into a 5 gallon bucket. It was one of my soapboxes when I worked at FSI and it continues to be one for me as I continue as one of their clients. Having been both an FAA and JAA examiner, I can say that the JAA exams are much more sane in terms of content. Their insanity falls into play when they require that the entire check be laid out for the applicant prior to the test. You can check chimpanzees that way. It's much more important to see how a crew responds to the unexpected rather than watch them recite a check ride script by rote.
But maybe that's just the curmudgeon in me.
Other than per FAR 25, it has to be equal to or greater than Vs, I can't offer much.
I do think that the problem still lies with the way that we train in bizjets. Because the FAA's infinite wisdom dictates that examiners and instructors concentrate on "filling the squares" of the Practical Test Standard, training in maneuvers like tire failure is generally not a priority. The fact is, that there is already so much to cover(much of it BS) that many instructors are always trying to put 20 gallons into a 5 gallon bucket. It was one of my soapboxes when I worked at FSI and it continues to be one for me as I continue as one of their clients. Having been both an FAA and JAA examiner, I can say that the JAA exams are much more sane in terms of content. Their insanity falls into play when they require that the entire check be laid out for the applicant prior to the test. You can check chimpanzees that way. It's much more important to see how a crew responds to the unexpected rather than watch them recite a check ride script by rote.
But maybe that's just the curmudgeon in me.
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dear 900 7X
your post echoes my own views on evaluating flight crews.
my question about min unstick speed would be the practical choice for a disabled plane to "jump" into the air and deal with problems in the sky instead of on the ground.
we all know, or SHOULD KNOW, that airplanes are at home in the air and only have the bare minimum of equipment for living on the ground.
this was best put to me many years ago by a wise writer who said/wrote:
airplane brakes are mickey mouse gadgets.
While there is no one answer , generally taking off is a better choice than stopping.
Of course one can look at the air france concorde and reject the above advice quite rightly.
what would Vs be...can you haul back and get into the air at 100 knots?
your post echoes my own views on evaluating flight crews.
my question about min unstick speed would be the practical choice for a disabled plane to "jump" into the air and deal with problems in the sky instead of on the ground.
we all know, or SHOULD KNOW, that airplanes are at home in the air and only have the bare minimum of equipment for living on the ground.
this was best put to me many years ago by a wise writer who said/wrote:
airplane brakes are mickey mouse gadgets.
While there is no one answer , generally taking off is a better choice than stopping.
Of course one can look at the air france concorde and reject the above advice quite rightly.
what would Vs be...can you haul back and get into the air at 100 knots?
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Lear 55 fire while parked in Omaha . . .
Sept. 30/ Lear 55 N824MG flew KMVY to KOMA, sometime after arriving, the aircraft while parked, caught fire for unknown reasons and burned.
It is listed as substantially damaged in FAA Preliminary Report.
IDENTIFICATION
Regis#: 824MG Make/Model: LJ55 Description:
Date: 09/30/2008 Time: 1757
Event Type: Accident Highest Injury: None Mid Air: N Missing: N
Damage: Substantial
LOCATION
City: OMAHA State: NE Country: US
DESCRIPTION
AIRCRAFT CAUGHT FIRE UNDER UNKNOWN CIRCUMSTANCES WHILE ON THE GROUND,
OMAHA, NE
It is listed as substantially damaged in FAA Preliminary Report.
IDENTIFICATION
Regis#: 824MG Make/Model: LJ55 Description:
Date: 09/30/2008 Time: 1757
Event Type: Accident Highest Injury: None Mid Air: N Missing: N
Damage: Substantial
LOCATION
City: OMAHA State: NE Country: US
DESCRIPTION
AIRCRAFT CAUGHT FIRE UNDER UNKNOWN CIRCUMSTANCES WHILE ON THE GROUND,
OMAHA, NE