Yeah, all three of those officers were my students. Sucks.Originally Posted by GJM
Yeah, all three of those officers were my students. Sucks.
Probably a stupid question, but couldn't this sort of testing be more safely done in ground effect over a very long runway?
Sorry to hear this. While eyewitness reports are often wrong, there was a report that the Eurocopter was following I15, at night, low level in poor weather and struck power lines.
Is the CH-53E typically flown IFR and does it have anti ice capability, or were they likely VFR with goggles?
Likes pretty much everything in every caliber.
I don't have much swept wing experience, but I would worry about a wing dropping, hitting the surface, and causing a crash.
Likes pretty much everything in every caliber.
oh good point.
100% IFR capable (actually, one of the only military aircraft with ILS capability) and we train significantly for IFR flight. 100% of Marine pilots are IFR rated and have annual minimums to meet for check rides or they get removed from flight status. Hard requirement.
That said, there’s only rudimentary autopilot functions on board the 53- namely, barometric altitude hold is pretty much the only function used, and most don’t like flying IFR if they don’t have to. We do teach a standard of contacting approach and picking up an IFR clearance if unable to maintain 200 AGL and above 60 kts. I’m not read in on the details, but if at night, most probably flying VFR with NVGs. This gets briefed pretty thoroughly in bad weather as the goggles allow visibility through light clouds and moisture due to a slight IR spectrum capability. This leads to the threat of not realizing you’re going IIMC until you’re there. Again, a known threat we always brief to.
The 53 does have anti ice capability but it’s limited to the engines. Blades tend to shed ice. Usually. It’s very scary when they don’t and I have a friend who lost a lot of altitude and tumbled end over end while spinning until the main and tail rotors finally shed the ice.
Oddlot,
Good catch with that Hawker find. I’m still trying to find out some info on both incidents. To expand on that article a bit... Sounds like whenever particular maintenance is done to flight control systems, Hawker requires you to verify stall characteristics. Reading between the lines, it appears that it might have an “older generation designed wing” that is unforgiving. Lots of times, a particular airplane model is “modernized” or stretched staying with the same basic airfoil design. This can lead to undesirable handling characteristics, that while still “legal” may differ from the original. The basic Hawker design has been around a long time. Reading that article, and reading the ADSB data available in this accident, this almost matches perfectly. Paul was a great guy, and while jumping to conclusions on this stuff is generally unseemly, I’m confident he wouldn’t mind us scratch our heads to figure it out. It looks like they may have taken off, got up to FL200 (recommended minimum altitude for this) slowed the plane up to check it, then it bit them. Reading that article it says that the stall speed may be 20+ knots off what it is supposed to be. That’s a bad surprise to get.
Swept wing jets can get gnarly in stalls. This is due to the sweep, and how the airflow separates during stalls. Many times, they will abruptly drop a wing and roll on their backs. With a T or crucifix style tail (which the Hawker is) it can develop into what’s called a “deep stall” in which the stabilizer is blanketed preventing lowering of the nose to recover, or in other cases a flat spin which often is unrecoverable. The last ADSB hit had the Hawker in (IIRC) a 16,000 foot per minute decent at about 80kts. They were falling straight down. Flat spin. To answer your question, this is to test stall speed and characteristics. It has to be done at altitude. It can’t be done in ground effect.
They will find out the cause. It’s another reason why this kind of crap (operational test flights) have no business being done by line pilots...no matter how much time in type they have. It should be left to the folks who’s job it is to investigate and test the dark corners of the envelope. If you don’t do this on a daily basis, it’s easy to miss clues the airplane might be telling you. At most airlines, they have a team of HIGHLY TRAINED pilots who pick up and test fly planes after maintenance. They are exposed to stuff in the sim and on actual flights that line pilots never see.
Working diligently to enlarge my group size.
Condolences to Entropy and TOTS. We had a large number of Class As across the DOD last year and unfortunately 2024 is already terrible. Fly safe everyone.
In general, high swept wings will stall at the tips and progress inwards towards the wing root. That means you lose effectiveness of the control surfaces at the wing tips first. That usually means ailerons are the first things you lose. So if you stall with any asymmetry and start dropping a wing, you could be along for the ride.
Some swept wings are designed with washout to reduce the wing tip angle of incidence (effectively less AOA at the tip, so the wing root will stall first or at least something more inboard).
Other band-aids are stall fences (remember the Mig 17), Vortex Generators, and my favorite, the Vortilon.
Thats just for roll. There are also pitch and yaw fixes. A great example, look at the empennage of the Beech 1900C vs the 1900D to see some "aero aids" (to be fair, these were more SEO considerations vice stall fixes AFAIK).
In experimental, in addition to the minimum altitudes, we expect a stable air mass. If we don't have the stable air mass, we don't test. I am not sure production test pilots have the luxury to say, "Nope, not today" unless its really bad. So yeah, we use RAWINSONDE data or borrow it (I can provide you a link if anyone is curious) + PIREPS etc.
I have a briefing somewhere from a US aviation company (99% of us have all flown their products) that will remain nameless, where they ran into major stall and post-stall negative characteristics on their new bizjet (mid 2000s). Its too expensive to redesign the wing (especially like Entropy said, when a jet is stretched or modified) so then you start adding the band-aids. So it happens, even with more modern designs.
Don't know if you want to see it, but there is a new dash cam video of the Florida incident from a semi just behind the landing.
Is there a typo or are you missing information here? I don't know for sure, but I'd think most military aircraft, at least fixed wing aircraft, have ILS capability, unless you meant to indicate rotary military aircraft.
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